diff --git a/composer.json b/composer.json
index 3aa7efe420ec0..632ebd9f63136 100644
--- a/composer.json
+++ b/composer.json
@@ -10,6 +10,7 @@
 		"issues": "https://core.trac.wordpress.org/"
 	},
 	"require": {
+		"ext-json": "*",
 		"php": ">=7.0"
 	},
 	"suggest": {
diff --git a/src/wp-includes/interactivity-api.php b/src/wp-includes/interactivity-api.php
deleted file mode 100644
index de9e877c9a761..0000000000000
--- a/src/wp-includes/interactivity-api.php
+++ /dev/null
@@ -1,26 +0,0 @@
-<?php
-/**
- * Interactivity API: Functions and hooks
- *
- * @package WordPress
- * @subpackage Interactivity API
- */
-
-/**
- * Registers the interactivity modules.
- */
-function wp_interactivity_register_script_modules() {
-	wp_register_script_module(
-		'@wordpress/interactivity',
-		includes_url( '/js/dist/interactivity.min.js' ),
-		array()
-	);
-
-	wp_register_script_module(
-		'@wordpress/interactivity-router',
-		includes_url( '/js/dist/interactivity-router.min.js' ),
-		array( '@wordpress/interactivity' )
-	);
-}
-
-add_action( 'init', 'wp_interactivity_register_script_modules' );
diff --git a/src/wp-includes/interactivity-api/class-wp-interactivity-api-directives-processor.php b/src/wp-includes/interactivity-api/class-wp-interactivity-api-directives-processor.php
new file mode 100644
index 0000000000000..24201e82fdd0a
--- /dev/null
+++ b/src/wp-includes/interactivity-api/class-wp-interactivity-api-directives-processor.php
@@ -0,0 +1,244 @@
+<?php
+/**
+ * Interactivity API: WP_Interactivity_API_Directives_Processor class.
+ *
+ * @package WordPress
+ * @subpackage Interactivity API
+ * @since 6.5.0
+ */
+
+/**
+ * Class used to iterate over the tags of an HTML string and help process the
+ * directive attributes.
+ *
+ * @since 6.5.0
+ *
+ * @access private
+ */
+final class WP_Interactivity_API_Directives_Processor extends WP_HTML_Tag_Processor {
+	/**
+	 * List of tags whose closer tag is not visited by the WP_HTML_Tag_Processor.
+	 *
+	 * @since 6.5.0
+	 * @var string[]
+	 */
+	const TAGS_THAT_DONT_VISIT_CLOSER_TAG = array(
+		'SCRIPT',
+		'IFRAME',
+		'NOEMBED',
+		'NOFRAMES',
+		'STYLE',
+		'TEXTAREA',
+		'TITLE',
+		'XMP',
+	);
+
+	/**
+	 * Returns the content between two balanced template tags.
+	 *
+	 * It positions the cursor in the closer tag of the balanced template tag,
+	 * if it exists.
+	 *
+	 * @since 6.5.0
+	 *
+	 * @access private
+	 *
+	 * @return string|null The content between the current opener template tag and its matching closer tag or null if it
+	 *                     doesn't find the matching closing tag or the current tag is not a template opener tag.
+	 */
+	public function get_content_between_balanced_template_tags() {
+		if ( 'TEMPLATE' !== $this->get_tag() ) {
+			return null;
+		}
+
+		$positions = $this->get_after_opener_tag_and_before_closer_tag_positions();
+		if ( ! $positions ) {
+			return null;
+		}
+		list( $after_opener_tag, $before_closer_tag ) = $positions;
+
+		return substr( $this->html, $after_opener_tag, $before_closer_tag - $after_opener_tag );
+	}
+
+	/**
+	 * Sets the content between two balanced tags.
+	 *
+	 * @since 6.5.0
+	 *
+	 * @access private
+	 *
+	 * @param string $new_content The string to replace the content between the matching tags.
+	 * @return bool Whether the content was successfully replaced.
+	 */
+	public function set_content_between_balanced_tags( string $new_content ): bool {
+		$positions = $this->get_after_opener_tag_and_before_closer_tag_positions( true );
+		if ( ! $positions ) {
+			return false;
+		}
+		list( $after_opener_tag, $before_closer_tag ) = $positions;
+
+		$this->lexical_updates[] = new WP_HTML_Text_Replacement(
+			$after_opener_tag,
+			$before_closer_tag - $after_opener_tag,
+			esc_html( $new_content )
+		);
+
+		return true;
+	}
+
+	/**
+	 * Appends content after the closing tag of a template tag.
+	 *
+	 * It positions the cursor in the closer tag of the balanced template tag,
+	 * if it exists.
+	 *
+	 * @access private
+	 *
+	 * @param string $new_content The string to append after the closing template tag.
+	 * @return bool Whether the content was successfully appended.
+	 */
+	public function append_content_after_template_tag_closer( string $new_content ): bool {
+		if ( empty( $new_content ) || 'TEMPLATE' !== $this->get_tag() || ! $this->is_tag_closer() ) {
+			return false;
+		}
+
+		// Flushes any changes.
+		$this->get_updated_html();
+
+		$bookmark = 'append_content_after_template_tag_closer';
+		$this->set_bookmark( $bookmark );
+		$after_closing_tag = $this->bookmarks[ $bookmark ]->start + $this->bookmarks[ $bookmark ]->length + 1;
+		$this->release_bookmark( $bookmark );
+
+		// Appends the new content.
+		$this->lexical_updates[] = new WP_HTML_Text_Replacement( $after_closing_tag, 0, $new_content );
+
+		return true;
+	}
+
+	/**
+	 * Gets the positions right after the opener tag and right before the closer
+	 * tag in a balanced tag.
+	 *
+	 * By default, it positions the cursor in the closer tag of the balanced tag.
+	 * If $rewind is true, it seeks back to the opener tag.
+	 *
+	 * @since 6.5.0
+	 *
+	 * @access private
+	 *
+	 * @param bool $rewind Optional. Whether to seek back to the opener tag after finding the positions. Defaults to false.
+	 * @return array|null Start and end byte position, or null when no balanced tag bookmarks.
+	 */
+	private function get_after_opener_tag_and_before_closer_tag_positions( bool $rewind = false ) {
+		// Flushes any changes.
+		$this->get_updated_html();
+
+		$bookmarks = $this->get_balanced_tag_bookmarks();
+		if ( ! $bookmarks ) {
+			return null;
+		}
+		list( $opener_tag, $closer_tag ) = $bookmarks;
+
+		$after_opener_tag  = $this->bookmarks[ $opener_tag ]->start + $this->bookmarks[ $opener_tag ]->length + 1;
+		$before_closer_tag = $this->bookmarks[ $closer_tag ]->start;
+
+		if ( $rewind ) {
+			$this->seek( $opener_tag );
+		}
+
+		$this->release_bookmark( $opener_tag );
+		$this->release_bookmark( $closer_tag );
+
+		return array( $after_opener_tag, $before_closer_tag );
+	}
+
+	/**
+	 * Returns a pair of bookmarks for the current opener tag and the matching
+	 * closer tag.
+	 *
+	 * It positions the cursor in the closer tag of the balanced tag, if it
+	 * exists.
+	 *
+	 * @since 6.5.0
+	 *
+	 * @return array|null A pair of bookmarks, or null if there's no matching closing tag.
+	 */
+	private function get_balanced_tag_bookmarks() {
+		static $i   = 0;
+		$opener_tag = 'opener_tag_of_balanced_tag_' . ++$i;
+
+		$this->set_bookmark( $opener_tag );
+		if ( ! $this->next_balanced_tag_closer_tag() ) {
+			$this->release_bookmark( $opener_tag );
+			return null;
+		}
+
+		$closer_tag = 'closer_tag_of_balanced_tag_' . ++$i;
+		$this->set_bookmark( $closer_tag );
+
+		return array( $opener_tag, $closer_tag );
+	}
+
+	/**
+	 * Finds the matching closing tag for an opening tag.
+	 *
+	 * When called while the processor is on an open tag, it traverses the HTML
+	 * until it finds the matching closer tag, respecting any in-between content,
+	 * including nested tags of the same name. Returns false when called on a
+	 * closer tag, a tag that doesn't have a closer tag (void), a tag that
+	 * doesn't visit the closer tag, or if no matching closing tag was found.
+	 *
+	 * @since 6.5.0
+	 *
+	 * @access private
+	 *
+	 * @return bool Whether a matching closing tag was found.
+	 */
+	public function next_balanced_tag_closer_tag(): bool {
+		$depth    = 0;
+		$tag_name = $this->get_tag();
+
+		if ( ! $this->has_and_visits_its_closer_tag() ) {
+			return false;
+		}
+
+		while ( $this->next_tag(
+			array(
+				'tag_name'    => $tag_name,
+				'tag_closers' => 'visit',
+			)
+		) ) {
+			if ( ! $this->is_tag_closer() ) {
+				++$depth;
+				continue;
+			}
+
+			if ( 0 === $depth ) {
+				return true;
+			}
+
+			--$depth;
+		}
+
+		return false;
+	}
+
+	/**
+	 * Checks whether the current tag has and will visit its matching closer tag.
+	 *
+	 * @since 6.5.0
+	 *
+	 * @access private
+	 *
+	 * @return bool Whether the current tag has a closer tag.
+	 */
+	public function has_and_visits_its_closer_tag(): bool {
+		$tag_name = $this->get_tag();
+
+		return null !== $tag_name && (
+			! WP_HTML_Processor::is_void( $tag_name ) &&
+			! in_array( $tag_name, self::TAGS_THAT_DONT_VISIT_CLOSER_TAG, true )
+		);
+	}
+}
diff --git a/src/wp-includes/interactivity-api/class-wp-interactivity-api.php b/src/wp-includes/interactivity-api/class-wp-interactivity-api.php
new file mode 100644
index 0000000000000..bb491a54f4ee2
--- /dev/null
+++ b/src/wp-includes/interactivity-api/class-wp-interactivity-api.php
@@ -0,0 +1,950 @@
+<?php
+/**
+ * Interactivity API: WP_Interactivity_API class.
+ *
+ * @package WordPress
+ * @subpackage Interactivity API
+ * @since 6.5.0
+ */
+
+/**
+ * Class used to process the Interactivity API on the server.
+ *
+ * @since 6.5.0
+ */
+final class WP_Interactivity_API {
+	/**
+	 * Holds the mapping of directive attribute names to their processor methods.
+	 *
+	 * @since 6.5.0
+	 * @var array
+	 */
+	private static $directive_processors = array(
+		'data-wp-interactive'   => 'data_wp_interactive_processor',
+		'data-wp-router-region' => 'data_wp_router_region_processor',
+		'data-wp-context'       => 'data_wp_context_processor',
+		'data-wp-bind'          => 'data_wp_bind_processor',
+		'data-wp-class'         => 'data_wp_class_processor',
+		'data-wp-style'         => 'data_wp_style_processor',
+		'data-wp-text'          => 'data_wp_text_processor',
+		/*
+		 * `data-wp-each` needs to be processed in the last place because it moves
+		 * the cursor to the end of the processed items to prevent them to be
+		 * processed twice.
+		 */
+		'data-wp-each'          => 'data_wp_each_processor',
+	);
+
+	/**
+	 * Holds the initial state of the different Interactivity API stores.
+	 *
+	 * This state is used during the server directive processing. Then, it is
+	 * serialized and sent to the client as part of the interactivity data to be
+	 * recovered during the hydration of the client interactivity stores.
+	 *
+	 * @since 6.5.0
+	 * @var array
+	 */
+	private $state_data = array();
+
+	/**
+	 * Holds the configuration required by the different Interactivity API stores.
+	 *
+	 * This configuration is serialized and sent to the client as part of the
+	 * interactivity data and can be accessed by the client interactivity stores.
+	 *
+	 * @since 6.5.0
+	 * @var array
+	 */
+	private $config_data = array();
+
+	/**
+	 * Flag that indicates whether the `data-wp-router-region` directive has
+	 * been found in the HTML and processed.
+	 *
+	 * The value is saved in a private property of the WP_Interactivity_API
+	 * instance instead of using a static variable inside the processor
+	 * function, which would hold the same value for all instances
+	 * independently of whether they have processed any
+	 * `data-wp-router-region` directive or not.
+	 *
+	 * @since 6.5.0
+	 * @var bool
+	 */
+	private $has_processed_router_region = false;
+
+	/**
+	 * Gets and/or sets the initial state of an Interactivity API store for a
+	 * given namespace.
+	 *
+	 * If state for that store namespace already exists, it merges the new
+	 * provided state with the existing one.
+	 *
+	 * @since 6.5.0
+	 *
+	 * @param string $store_namespace The unique store namespace identifier.
+	 * @param array  $state           Optional. The array that will be merged with the existing state for the specified
+	 *                                store namespace.
+	 * @return array The current state for the specified store namespace. This will be the updated state if a $state
+	 *               argument was provided.
+	 */
+	public function state( string $store_namespace, array $state = array() ): array {
+		if ( ! isset( $this->state_data[ $store_namespace ] ) ) {
+			$this->state_data[ $store_namespace ] = array();
+		}
+		if ( is_array( $state ) ) {
+			$this->state_data[ $store_namespace ] = array_replace_recursive(
+				$this->state_data[ $store_namespace ],
+				$state
+			);
+		}
+		return $this->state_data[ $store_namespace ];
+	}
+
+	/**
+	 * Gets and/or sets the configuration of the Interactivity API for a given
+	 * store namespace.
+	 *
+	 * If configuration for that store namespace exists, it merges the new
+	 * provided configuration with the existing one.
+	 *
+	 * @since 6.5.0
+	 *
+	 * @param string $store_namespace The unique store namespace identifier.
+	 * @param array  $config          Optional. The array that will be merged with the existing configuration for the
+	 *                                specified store namespace.
+	 * @return array The configuration for the specified store namespace. This will be the updated configuration if a
+	 *               $config argument was provided.
+	 */
+	public function config( string $store_namespace, array $config = array() ): array {
+		if ( ! isset( $this->config_data[ $store_namespace ] ) ) {
+			$this->config_data[ $store_namespace ] = array();
+		}
+		if ( is_array( $config ) ) {
+			$this->config_data[ $store_namespace ] = array_replace_recursive(
+				$this->config_data[ $store_namespace ],
+				$config
+			);
+		}
+		return $this->config_data[ $store_namespace ];
+	}
+
+	/**
+	 * Prints the serialized client-side interactivity data.
+	 *
+	 * Encodes the config and initial state into JSON and prints them inside a
+	 * script tag of type "application/json". Once in the browser, the state will
+	 * be parsed and used to hydrate the client-side interactivity stores and the
+	 * configuration will be available using a `getConfig` utility.
+	 *
+	 * @since 6.5.0
+	 */
+	public function print_client_interactivity_data() {
+		$store      = array();
+		$has_state  = ! empty( $this->state_data );
+		$has_config = ! empty( $this->config_data );
+
+		if ( $has_state || $has_config ) {
+			if ( $has_config ) {
+				$store['config'] = $this->config_data;
+			}
+			if ( $has_state ) {
+				$store['state'] = $this->state_data;
+			}
+			wp_print_inline_script_tag(
+				wp_json_encode(
+					$store,
+					JSON_HEX_TAG | JSON_HEX_AMP
+				),
+				array(
+					'type' => 'application/json',
+					'id'   => 'wp-interactivity-data',
+				)
+			);
+		}
+	}
+
+	/**
+	 * Registers the `@wordpress/interactivity` script modules.
+	 *
+	 * @since 6.5.0
+	 */
+	public function register_script_modules() {
+		$suffix = wp_scripts_get_suffix();
+
+		wp_register_script_module(
+			'@wordpress/interactivity',
+			includes_url( "js/dist/interactivity$suffix.js" )
+		);
+
+		wp_register_script_module(
+			'@wordpress/interactivity-router',
+			includes_url( "js/dist/interactivity-router$suffix.js" ),
+			array( '@wordpress/interactivity' )
+		);
+	}
+
+	/**
+	 * Adds the necessary hooks for the Interactivity API.
+	 *
+	 * @since 6.5.0
+	 */
+	public function add_hooks() {
+		add_action( 'wp_enqueue_scripts', array( $this, 'register_script_modules' ) );
+		add_action( 'wp_footer', array( $this, 'print_client_interactivity_data' ) );
+	}
+
+	/**
+	 * Processes the interactivity directives contained within the HTML content
+	 * and updates the markup accordingly.
+	 *
+	 * @since 6.5.0
+	 *
+	 * @param string $html The HTML content to process.
+	 * @return string The processed HTML content. It returns the original content when the HTML contains unbalanced tags.
+	 */
+	public function process_directives( string $html ): string {
+		$context_stack   = array();
+		$namespace_stack = array();
+		$result          = $this->process_directives_args( $html, $context_stack, $namespace_stack );
+		return null === $result ? $html : $result;
+	}
+
+	/**
+	 * Processes the interactivity directives contained within the HTML content
+	 * and updates the markup accordingly.
+	 *
+	 * It needs the context and namespace stacks to be passed by reference, and
+	 * it returns null if the HTML contains unbalanced tags.
+	 *
+	 * @since 6.5.0
+	 *
+	 * @param string $html            The HTML content to process.
+	 * @param array  $context_stack   The reference to the array used to keep track of contexts during processing.
+	 * @param array  $namespace_stack The reference to the array used to manage namespaces during processing.
+	 * @return string|null The processed HTML content. It returns null when the HTML contains unbalanced tags.
+	 */
+	private function process_directives_args( string $html, array &$context_stack, array &$namespace_stack ) {
+		$p          = new WP_Interactivity_API_Directives_Processor( $html );
+		$tag_stack  = array();
+		$unbalanced = false;
+
+		$directive_processor_prefixes          = array_keys( self::$directive_processors );
+		$directive_processor_prefixes_reversed = array_reverse( $directive_processor_prefixes );
+
+		while ( $p->next_tag( array( 'tag_closers' => 'visit' ) ) ) {
+			$tag_name = $p->get_tag();
+
+			if ( 'SVG' === $tag_name || 'MATH' === $tag_name ) {
+				$unbalanced = true;
+				break;
+			}
+
+			if ( $p->is_tag_closer() ) {
+				list( $opening_tag_name, $directives_prefixes ) = end( $tag_stack );
+
+				if ( 0 === count( $tag_stack ) || $opening_tag_name !== $tag_name ) {
+
+					/*
+					 * If the tag stack is empty or the matching opening tag is not the
+					 * same than the closing tag, it means the HTML is unbalanced and it
+					 * stops processing it.
+					 */
+					$unbalanced = true;
+					break;
+				} else {
+					// Remove the last tag from the stack.
+					array_pop( $tag_stack );
+				}
+			} else {
+				if ( 0 !== count( $p->get_attribute_names_with_prefix( 'data-wp-each-child' ) ) ) {
+					/*
+					 * If the tag has a `data-wp-each-child` directive, jump to its closer
+					 * tag because those tags have already been processed.
+					 */
+					$p->next_balanced_tag_closer_tag();
+					continue;
+				} else {
+					$directives_prefixes = array();
+
+					// Checks if there is a server directive processor registered for each directive.
+					foreach ( $p->get_attribute_names_with_prefix( 'data-wp-' ) as $attribute_name ) {
+						list( $directive_prefix ) = $this->extract_prefix_and_suffix( $attribute_name );
+						if ( array_key_exists( $directive_prefix, self::$directive_processors ) ) {
+							$directives_prefixes[] = $directive_prefix;
+						}
+					}
+
+					/*
+					 * If this tag will visit its closer tag, it adds it to the tag stack
+					 * so it can process its closing tag and check for unbalanced tags.
+					 */
+					if ( $p->has_and_visits_its_closer_tag() ) {
+						$tag_stack[] = array( $tag_name, $directives_prefixes );
+					}
+				}
+			}
+			/*
+				* If the matching opener tag didn't have any directives, it can skip the
+				* processing.
+				*/
+			if ( 0 === count( $directives_prefixes ) ) {
+				continue;
+			}
+
+			/*
+			 * Sorts the attributes by the order of the `directives_processor` array
+			 * and checks what directives are present in this element. The processing
+			 * order is reversed for tag closers.
+			 */
+			$directives_prefixes = array_intersect(
+				$p->is_tag_closer()
+					? $directive_processor_prefixes_reversed
+					: $directive_processor_prefixes,
+				$directives_prefixes
+			);
+
+			// Executes the directive processors present in this element.
+			foreach ( $directives_prefixes as $directive_prefix ) {
+				$func = is_array( self::$directive_processors[ $directive_prefix ] )
+					? self::$directive_processors[ $directive_prefix ]
+					: array( $this, self::$directive_processors[ $directive_prefix ] );
+				call_user_func_array(
+					$func,
+					array( $p, &$context_stack, &$namespace_stack, &$tag_stack )
+				);
+			}
+		}
+
+		/*
+		 * It returns null if the HTML is unbalanced because unbalanced HTML is
+		 * not safe to process. In that case, the Interactivity API runtime will
+		 * update the HTML on the client side during the hydration.
+		 */
+		return $unbalanced || 0 < count( $tag_stack ) ? null : $p->get_updated_html();
+	}
+
+	/**
+	 * Evaluates the reference path passed to a directive based on the current
+	 * store namespace, state and context.
+	 *
+	 * @since 6.5.0
+	 *
+	 * @param string|true $directive_value   The directive attribute value string or `true` when it's a boolean attribute.
+	 * @param string      $default_namespace The default namespace to use if none is explicitly defined in the directive
+	 *                                       value.
+	 * @param array|false $context           The current context for evaluating the directive or false if there is no
+	 *                                       context.
+	 * @return mixed|null The result of the evaluation. Null if the reference path doesn't exist.
+	 */
+	private function evaluate( $directive_value, string $default_namespace, $context = false ) {
+		list( $ns, $path ) = $this->extract_directive_value( $directive_value, $default_namespace );
+		if ( empty( $path ) ) {
+			return null;
+		}
+
+		$store = array(
+			'state'   => $this->state_data[ $ns ] ?? array(),
+			'context' => $context[ $ns ] ?? array(),
+		);
+
+		// Checks if the reference path is preceded by a negation operator (!).
+		$should_negate_value = '!' === $path[0];
+		$path                = $should_negate_value ? substr( $path, 1 ) : $path;
+
+		// Extracts the value from the store using the reference path.
+		$path_segments = explode( '.', $path );
+		$current       = $store;
+		foreach ( $path_segments as $path_segment ) {
+			if ( isset( $current[ $path_segment ] ) ) {
+				$current = $current[ $path_segment ];
+			} else {
+				return null;
+			}
+		}
+
+		// Returns the opposite if it contains a negation operator (!).
+		return $should_negate_value ? ! $current : $current;
+	}
+
+	/**
+	 * Extracts the directive attribute name to separate and return the directive
+	 * prefix and an optional suffix.
+	 *
+	 * The suffix is the string after the first double hyphen and the prefix is
+	 * everything that comes before the suffix.
+	 *
+	 * Example:
+	 *
+	 *     extract_prefix_and_suffix( 'data-wp-interactive' )   => array( 'data-wp-interactive', null )
+	 *     extract_prefix_and_suffix( 'data-wp-bind--src' )     => array( 'data-wp-bind', 'src' )
+	 *     extract_prefix_and_suffix( 'data-wp-foo--and--bar' ) => array( 'data-wp-foo', 'and--bar' )
+	 *
+	 * @since 6.5.0
+	 *
+	 * @param string $directive_name The directive attribute name.
+	 * @return array An array containing the directive prefix and optional suffix.
+	 */
+	private function extract_prefix_and_suffix( string $directive_name ): array {
+		return explode( '--', $directive_name, 2 );
+	}
+
+	/**
+	 * Parses and extracts the namespace and reference path from the given
+	 * directive attribute value.
+	 *
+	 * If the value doesn't contain an explicit namespace, it returns the
+	 * default one. If the value contains a JSON object instead of a reference
+	 * path, the function tries to parse it and return the resulting array. If
+	 * the value contains strings that represent booleans ("true" and "false"),
+	 * numbers ("1" and "1.2") or "null", the function also transform them to
+	 * regular booleans, numbers and `null`.
+	 *
+	 * Example:
+	 *
+	 *     extract_directive_value( 'actions.foo', 'myPlugin' )                      => array( 'myPlugin', 'actions.foo' )
+	 *     extract_directive_value( 'otherPlugin::actions.foo', 'myPlugin' )         => array( 'otherPlugin', 'actions.foo' )
+	 *     extract_directive_value( '{ "isOpen": false }', 'myPlugin' )              => array( 'myPlugin', array( 'isOpen' => false ) )
+	 *     extract_directive_value( 'otherPlugin::{ "isOpen": false }', 'myPlugin' ) => array( 'otherPlugin', array( 'isOpen' => false ) )
+	 *
+	 * @since 6.5.0
+	 *
+	 * @param string|true $directive_value   The directive attribute value. It can be `true` when it's a boolean
+	 *                                       attribute.
+	 * @param string|null $default_namespace Optional. The default namespace if none is explicitly defined.
+	 * @return array An array containing the namespace in the first item and the JSON, the reference path, or null on the
+	 *               second item.
+	 */
+	private function extract_directive_value( $directive_value, $default_namespace = null ): array {
+		if ( empty( $directive_value ) || is_bool( $directive_value ) ) {
+			return array( $default_namespace, null );
+		}
+
+		// Replaces the value and namespace if there is a namespace in the value.
+		if ( 1 === preg_match( '/^([\w\-_\/]+)::./', $directive_value ) ) {
+			list($default_namespace, $directive_value) = explode( '::', $directive_value, 2 );
+		}
+
+		/*
+		 * Tries to decode the value as a JSON object. If it fails and the value
+		 * isn't `null`, it returns the value as it is. Otherwise, it returns the
+		 * decoded JSON or null for the string `null`.
+		 */
+		$decoded_json = json_decode( $directive_value, true );
+		if ( null !== $decoded_json || 'null' === $directive_value ) {
+			$directive_value = $decoded_json;
+		}
+
+		return array( $default_namespace, $directive_value );
+	}
+
+	/**
+	 * Transforms a kebab-case string to camelCase.
+	 *
+	 * @param string $str The kebab-case string to transform to camelCase.
+	 * @return string The transformed camelCase string.
+	 */
+	private function kebab_to_camel_case( string $str ): string {
+		return lcfirst(
+			preg_replace_callback(
+				'/(-)([a-z])/',
+				function ( $matches ) {
+					return strtoupper( $matches[2] );
+				},
+				strtolower( rtrim( $str, '-' ) )
+			)
+		);
+	}
+
+	/**
+	 * Processes the `data-wp-interactive` directive.
+	 *
+	 * It adds the default store namespace defined in the directive value to the
+	 * stack so that it's available for the nested interactivity elements.
+	 *
+	 * @since 6.5.0
+	 *
+	 * @param WP_Interactivity_API_Directives_Processor $p               The directives processor instance.
+	 * @param array                                     $context_stack   The reference to the context stack.
+	 * @param array                                     $namespace_stack The reference to the store namespace stack.
+	 */
+	private function data_wp_interactive_processor( WP_Interactivity_API_Directives_Processor $p, array &$context_stack, array &$namespace_stack ) {
+		// In closing tags, it removes the last namespace from the stack.
+		if ( $p->is_tag_closer() ) {
+			array_pop( $namespace_stack );
+			return;
+		}
+
+		// Tries to decode the `data-wp-interactive` attribute value.
+		$attribute_value = $p->get_attribute( 'data-wp-interactive' );
+
+		/*
+		 * Pushes the newly defined namespace or the current one if the
+		 * `data-wp-interactive` definition was invalid or does not contain a
+		 * namespace. It does so because the function pops out the current namespace
+		 * from the stack whenever it finds a `data-wp-interactive`'s closing tag,
+		 * independently of whether the previous `data-wp-interactive` definition
+		 * contained a valid namespace.
+		 */
+		$new_namespace = null;
+		if ( is_string( $attribute_value ) && ! empty( $attribute_value ) ) {
+			$decoded_json = json_decode( $attribute_value, true );
+			if ( is_array( $decoded_json ) ) {
+				$new_namespace = $decoded_json['namespace'] ?? null;
+			} else {
+				$new_namespace = $attribute_value;
+			}
+		}
+		$namespace_stack[] = ( $new_namespace && 1 === preg_match( '/^([\w\-_\/]+)/', $new_namespace ) )
+			? $new_namespace
+			: end( $namespace_stack );
+	}
+
+	/**
+	 * Processes the `data-wp-context` directive.
+	 *
+	 * It adds the context defined in the directive value to the stack so that
+	 * it's available for the nested interactivity elements.
+	 *
+	 * @since 6.5.0
+	 *
+	 * @param WP_Interactivity_API_Directives_Processor $p               The directives processor instance.
+	 * @param array                                     $context_stack   The reference to the context stack.
+	 * @param array                                     $namespace_stack The reference to the store namespace stack.
+	 */
+	private function data_wp_context_processor( WP_Interactivity_API_Directives_Processor $p, array &$context_stack, array &$namespace_stack ) {
+		// In closing tags, it removes the last context from the stack.
+		if ( $p->is_tag_closer() ) {
+			array_pop( $context_stack );
+			return;
+		}
+
+		$attribute_value = $p->get_attribute( 'data-wp-context' );
+		$namespace_value = end( $namespace_stack );
+
+		// Separates the namespace from the context JSON object.
+		list( $namespace_value, $decoded_json ) = is_string( $attribute_value ) && ! empty( $attribute_value )
+			? $this->extract_directive_value( $attribute_value, $namespace_value )
+			: array( $namespace_value, null );
+
+		/*
+		 * If there is a namespace, it adds a new context to the stack merging the
+		 * previous context with the new one.
+		 */
+		if ( is_string( $namespace_value ) ) {
+			$context_stack[] = array_replace_recursive(
+				end( $context_stack ) !== false ? end( $context_stack ) : array(),
+				array( $namespace_value => is_array( $decoded_json ) ? $decoded_json : array() )
+			);
+		} else {
+			/*
+			 * If there is no namespace, it pushes the current context to the stack.
+			 * It needs to do so because the function pops out the current context
+			 * from the stack whenever it finds a `data-wp-context`'s closing tag.
+			 */
+			$context_stack[] = end( $context_stack );
+		}
+	}
+
+	/**
+	 * Processes the `data-wp-bind` directive.
+	 *
+	 * It updates or removes the bound attributes based on the evaluation of its
+	 * associated reference.
+	 *
+	 * @since 6.5.0
+	 *
+	 * @param WP_Interactivity_API_Directives_Processor $p               The directives processor instance.
+	 * @param array                                     $context_stack   The reference to the context stack.
+	 * @param array                                     $namespace_stack The reference to the store namespace stack.
+	 */
+	private function data_wp_bind_processor( WP_Interactivity_API_Directives_Processor $p, array &$context_stack, array &$namespace_stack ) {
+		if ( ! $p->is_tag_closer() ) {
+			$all_bind_directives = $p->get_attribute_names_with_prefix( 'data-wp-bind--' );
+
+			foreach ( $all_bind_directives as $attribute_name ) {
+				list( , $bound_attribute ) = $this->extract_prefix_and_suffix( $attribute_name );
+				if ( empty( $bound_attribute ) ) {
+					return;
+				}
+
+				$attribute_value = $p->get_attribute( $attribute_name );
+				$result          = $this->evaluate( $attribute_value, end( $namespace_stack ), end( $context_stack ) );
+
+				if ( null !== $result && ( false !== $result || '-' === $bound_attribute[4] ) ) {
+					/*
+					 * If the result of the evaluation is a boolean and the attribute is
+					 * `aria-` or `data-, convert it to a string "true" or "false". It
+					 * follows the exact same logic as Preact because it needs to
+					 * replicate what Preact will later do in the client:
+					 * https://github.com/preactjs/preact/blob/ea49f7a0f9d1ff2c98c0bdd66aa0cbc583055246/src/diff/props.js#L131C24-L136
+					 */
+					if ( is_bool( $result ) && '-' === $bound_attribute[4] ) {
+						$result = $result ? 'true' : 'false';
+					}
+					$p->set_attribute( $bound_attribute, $result );
+				} else {
+					$p->remove_attribute( $bound_attribute );
+				}
+			}
+		}
+	}
+
+	/**
+	 * Processes the `data-wp-class` directive.
+	 *
+	 * It adds or removes CSS classes in the current HTML element based on the
+	 * evaluation of its associated references.
+	 *
+	 * @since 6.5.0
+	 *
+	 * @param WP_Interactivity_API_Directives_Processor $p               The directives processor instance.
+	 * @param array                                     $context_stack   The reference to the context stack.
+	 * @param array                                     $namespace_stack The reference to the store namespace stack.
+	 */
+	private function data_wp_class_processor( WP_Interactivity_API_Directives_Processor $p, array &$context_stack, array &$namespace_stack ) {
+		if ( ! $p->is_tag_closer() ) {
+			$all_class_directives = $p->get_attribute_names_with_prefix( 'data-wp-class--' );
+
+			foreach ( $all_class_directives as $attribute_name ) {
+				list( , $class_name ) = $this->extract_prefix_and_suffix( $attribute_name );
+				if ( empty( $class_name ) ) {
+					return;
+				}
+
+				$attribute_value = $p->get_attribute( $attribute_name );
+				$result          = $this->evaluate( $attribute_value, end( $namespace_stack ), end( $context_stack ) );
+
+				if ( $result ) {
+					$p->add_class( $class_name );
+				} else {
+					$p->remove_class( $class_name );
+				}
+			}
+		}
+	}
+
+	/**
+	 * Processes the `data-wp-style` directive.
+	 *
+	 * It updates the style attribute value of the current HTML element based on
+	 * the evaluation of its associated references.
+	 *
+	 * @since 6.5.0
+	 *
+	 * @param WP_Interactivity_API_Directives_Processor $p               The directives processor instance.
+	 * @param array                                     $context_stack   The reference to the context stack.
+	 * @param array                                     $namespace_stack The reference to the store namespace stack.
+	 */
+	private function data_wp_style_processor( WP_Interactivity_API_Directives_Processor $p, array &$context_stack, array &$namespace_stack ) {
+		if ( ! $p->is_tag_closer() ) {
+			$all_style_attributes = $p->get_attribute_names_with_prefix( 'data-wp-style--' );
+
+			foreach ( $all_style_attributes as $attribute_name ) {
+				list( , $style_property ) = $this->extract_prefix_and_suffix( $attribute_name );
+				if ( empty( $style_property ) ) {
+					continue;
+				}
+
+				$directive_attribute_value = $p->get_attribute( $attribute_name );
+				$style_property_value      = $this->evaluate( $directive_attribute_value, end( $namespace_stack ), end( $context_stack ) );
+				$style_attribute_value     = $p->get_attribute( 'style' );
+				$style_attribute_value     = ( $style_attribute_value && ! is_bool( $style_attribute_value ) ) ? $style_attribute_value : '';
+
+				/*
+				 * Checks first if the style property is not falsy and the style
+				 * attribute value is not empty because if it is, it doesn't need to
+				 * update the attribute value.
+				 */
+				if ( $style_property_value || $style_attribute_value ) {
+					$style_attribute_value = $this->merge_style_property( $style_attribute_value, $style_property, $style_property_value );
+					/*
+					 * If the style attribute value is not empty, it sets it. Otherwise,
+					 * it removes it.
+					 */
+					if ( ! empty( $style_attribute_value ) ) {
+						$p->set_attribute( 'style', $style_attribute_value );
+					} else {
+						$p->remove_attribute( 'style' );
+					}
+				}
+			}
+		}
+	}
+
+	/**
+	 * Merges an individual style property in the `style` attribute of an HTML
+	 * element, updating or removing the property when necessary.
+	 *
+	 * If a property is modified, the old one is removed and the new one is added
+	 * at the end of the list.
+	 *
+	 * @since 6.5.0
+	 *
+	 * Example:
+	 *
+	 *     merge_style_property( 'color:green;', 'color', 'red' )      => 'color:red;'
+	 *     merge_style_property( 'background:green;', 'color', 'red' ) => 'background:green;color:red;'
+	 *     merge_style_property( 'color:green;', 'color', null )       => ''
+	 *
+	 * @param string            $style_attribute_value The current style attribute value.
+	 * @param string            $style_property_name   The style property name to set.
+	 * @param string|false|null $style_property_value  The value to set for the style property. With false, null or an
+	 *                                                 empty string, it removes the style property.
+	 * @return string The new style attribute value after the specified property has been added, updated or removed.
+	 */
+	private function merge_style_property( string $style_attribute_value, string $style_property_name, $style_property_value ): string {
+		$style_assignments    = explode( ';', $style_attribute_value );
+		$result               = array();
+		$style_property_value = ! empty( $style_property_value ) ? rtrim( trim( $style_property_value ), ';' ) : null;
+		$new_style_property   = $style_property_value ? $style_property_name . ':' . $style_property_value . ';' : '';
+
+		// Generates an array with all the properties but the modified one.
+		foreach ( $style_assignments as $style_assignment ) {
+			if ( empty( trim( $style_assignment ) ) ) {
+				continue;
+			}
+			list( $name, $value ) = explode( ':', $style_assignment );
+			if ( trim( $name ) !== $style_property_name ) {
+				$result[] = trim( $name ) . ':' . trim( $value ) . ';';
+			}
+		}
+
+		// Adds the new/modified property at the end of the list.
+		$result[] = $new_style_property;
+
+		return implode( '', $result );
+	}
+
+	/**
+	 * Processes the `data-wp-text` directive.
+	 *
+	 * It updates the inner content of the current HTML element based on the
+	 * evaluation of its associated reference.
+	 *
+	 * @since 6.5.0
+	 *
+	 * @param WP_Interactivity_API_Directives_Processor $p               The directives processor instance.
+	 * @param array                                     $context_stack   The reference to the context stack.
+	 * @param array                                     $namespace_stack The reference to the store namespace stack.
+	 */
+	private function data_wp_text_processor( WP_Interactivity_API_Directives_Processor $p, array &$context_stack, array &$namespace_stack ) {
+		if ( ! $p->is_tag_closer() ) {
+			$attribute_value = $p->get_attribute( 'data-wp-text' );
+			$result          = $this->evaluate( $attribute_value, end( $namespace_stack ), end( $context_stack ) );
+
+			/*
+			 * Follows the same logic as Preact in the client and only changes the
+			 * content if the value is a string or a number. Otherwise, it removes the
+			 * content.
+			 */
+			if ( is_string( $result ) || is_numeric( $result ) ) {
+				$p->set_content_between_balanced_tags( esc_html( $result ) );
+			} else {
+				$p->set_content_between_balanced_tags( '' );
+			}
+		}
+	}
+
+	/**
+	 * Returns the CSS styles for animating the top loading bar in the router.
+	 *
+	 * @since 6.5.0
+	 *
+	 * @return string The CSS styles for the router's top loading bar animation.
+	 */
+	private function get_router_animation_styles(): string {
+		return <<<CSS
+			.wp-interactivity-router-loading-bar {
+				position: fixed;
+				top: 0;
+				left: 0;
+				margin: 0;
+				padding: 0;
+				width: 100vw;
+				max-width: 100vw !important;
+				height: 4px;
+				background-color: #000;
+				opacity: 0
+			}
+			.wp-interactivity-router-loading-bar.start-animation {
+				animation: wp-interactivity-router-loading-bar-start-animation 30s cubic-bezier(0.03, 0.5, 0, 1) forwards
+			}
+			.wp-interactivity-router-loading-bar.finish-animation {
+				animation: wp-interactivity-router-loading-bar-finish-animation 300ms ease-in
+			}
+			@keyframes wp-interactivity-router-loading-bar-start-animation {
+				0% { transform: scaleX(0); transform-origin: 0 0; opacity: 1 }
+				100% { transform: scaleX(1); transform-origin: 0 0; opacity: 1 }
+			}
+			@keyframes wp-interactivity-router-loading-bar-finish-animation {
+				0% { opacity: 1 }
+				50% { opacity: 1 }
+				100% { opacity: 0 }
+			}
+CSS;
+	}
+
+	/**
+	 * Outputs the markup for the top loading indicator and the screen reader
+	 * notifications during client-side navigations.
+	 *
+	 * This method prints a div element representing a loading bar visible during
+	 * navigation, as well as an aria-live region that can be read by screen
+	 * readers to announce navigation status.
+	 *
+	 * @since 6.5.0
+	 */
+	public function print_router_loading_and_screen_reader_markup() {
+		echo <<<HTML
+			<div
+				class="wp-interactivity-router-loading-bar"
+				data-wp-interactive='{"namespace":"core/router"}'
+				data-wp-class--start-animation="state.navigation.hasStarted"
+				data-wp-class--finish-animation="state.navigation.hasFinished"
+			></div>
+			<div
+				class="screen-reader-text"
+				aria-live="polite"
+				data-wp-interactive='{"namespace":"core/router"}'
+				data-wp-text="state.navigation.message"
+			></div>
+HTML;
+	}
+
+	/**
+	 * Processes the `data-wp-router-region` directive.
+	 *
+	 * It renders in the footer a set of HTML elements to notify users about
+	 * client-side navigations. More concretely, the elements added are 1) a
+	 * top loading bar to visually inform that a navigation is in progress
+	 * and 2) an `aria-live` region for accessible navigation announcements.
+	 *
+	 * @since 6.5.0
+	 *
+	 * @param WP_Interactivity_API_Directives_Processor $p The directives processor instance.
+	 */
+	private function data_wp_router_region_processor( WP_Interactivity_API_Directives_Processor $p ) {
+		if ( ! $p->is_tag_closer() && ! $this->has_processed_router_region ) {
+			$this->has_processed_router_region = true;
+
+			// Initialize the `core/router` store.
+			$this->state(
+				'core/router',
+				array(
+					'navigation' => array(
+						'texts' => array(
+							'loading' => __( 'Loading page, please wait.' ),
+							'loaded'  => __( 'Page Loaded.' ),
+						),
+					),
+				)
+			);
+
+			// Enqueues as an inline style.
+			wp_register_style( 'wp-interactivity-router-animations', false );
+			wp_add_inline_style( 'wp-interactivity-router-animations', $this->get_router_animation_styles() );
+			wp_enqueue_style( 'wp-interactivity-router-animations' );
+
+			// Adds the necessary markup to the footer.
+			add_action( 'wp_footer', array( $this, 'print_router_loading_and_screen_reader_markup' ) );
+		}
+	}
+
+	/**
+	 * Processes the `data-wp-each` directive.
+	 *
+	 * This directive gets an array passed as reference and iterates over it
+	 * generating new content for each item based on the inner markup of the
+	 * `template` tag.
+	 *
+	 * @since 6.5.0
+	 *
+	 * @param WP_Interactivity_API_Directives_Processor $p               The directives processor instance.
+	 * @param array                                     $context_stack   The reference to the context stack.
+	 * @param array                                     $namespace_stack The reference to the store namespace stack.
+	 * @param array                                     $tag_stack       The reference to the tag stack.
+	 */
+	private function data_wp_each_processor( WP_Interactivity_API_Directives_Processor $p, array &$context_stack, array &$namespace_stack, array &$tag_stack ) {
+		if ( ! $p->is_tag_closer() && 'TEMPLATE' === $p->get_tag() ) {
+			$attribute_name   = $p->get_attribute_names_with_prefix( 'data-wp-each' )[0];
+			$extracted_suffix = $this->extract_prefix_and_suffix( $attribute_name );
+			$item_name        = isset( $extracted_suffix[1] ) ? $this->kebab_to_camel_case( $extracted_suffix[1] ) : 'item';
+			$attribute_value  = $p->get_attribute( $attribute_name );
+			$result           = $this->evaluate( $attribute_value, end( $namespace_stack ), end( $context_stack ) );
+
+			// Gets the content between the template tags and leaves the cursor in the closer tag.
+			$inner_content = $p->get_content_between_balanced_template_tags();
+
+			// Checks if there is a manual server-side directive processing.
+			$template_end = 'data-wp-each: template end';
+			$p->set_bookmark( $template_end );
+			$p->next_tag();
+			$manual_sdp = $p->get_attribute( 'data-wp-each-child' );
+			$p->seek( $template_end ); // Rewinds to the template closer tag.
+			$p->release_bookmark( $template_end );
+
+			/*
+			 * It doesn't process in these situations:
+			 * - Manual server-side directive processing.
+			 * - Empty or non-array values.
+			 * - Associative arrays because those are deserialized as objects in JS.
+			 * - Templates that contain top-level texts because those texts can't be
+			 *   identified and removed in the client.
+			 */
+			if (
+				$manual_sdp ||
+				empty( $result ) ||
+				! is_array( $result ) ||
+				! array_is_list( $result ) ||
+				! str_starts_with( trim( $inner_content ), '<' ) ||
+				! str_ends_with( trim( $inner_content ), '>' )
+			) {
+				array_pop( $tag_stack );
+				return;
+			}
+
+			// Extracts the namespace from the directive attribute value.
+			$namespace_value         = end( $namespace_stack );
+			list( $namespace_value ) = is_string( $attribute_value ) && ! empty( $attribute_value )
+				? $this->extract_directive_value( $attribute_value, $namespace_value )
+				: array( $namespace_value, null );
+
+			// Processes the inner content for each item of the array.
+			$processed_content = '';
+			foreach ( $result as $item ) {
+				// Creates a new context that includes the current item of the array.
+				$context_stack[] = array_replace_recursive(
+					end( $context_stack ) !== false ? end( $context_stack ) : array(),
+					array( $namespace_value => array( $item_name => $item ) )
+				);
+
+				// Processes the inner content with the new context.
+				$processed_item = $this->process_directives_args( $inner_content, $context_stack, $namespace_stack );
+
+				if ( null === $processed_item ) {
+					// If the HTML is unbalanced, stop processing it.
+					array_pop( $context_stack );
+					return;
+				}
+
+				// Adds the `data-wp-each-child` to each top-level tag.
+				$i = new WP_Interactivity_API_Directives_Processor( $processed_item );
+				while ( $i->next_tag() ) {
+					$i->set_attribute( 'data-wp-each-child', true );
+					$i->next_balanced_tag_closer_tag();
+				}
+				$processed_content .= $i->get_updated_html();
+
+				// Removes the current context from the stack.
+				array_pop( $context_stack );
+			}
+
+			// Appends the processed content after the tag closer of the template.
+			$p->append_content_after_template_tag_closer( $processed_content );
+
+			// Pops the last tag because it skipped the closing tag of the template tag.
+			array_pop( $tag_stack );
+		}
+	}
+}
diff --git a/src/wp-includes/interactivity-api/interactivity-api.php b/src/wp-includes/interactivity-api/interactivity-api.php
new file mode 100644
index 0000000000000..548fcc3638fb7
--- /dev/null
+++ b/src/wp-includes/interactivity-api/interactivity-api.php
@@ -0,0 +1,166 @@
+<?php
+/**
+ * Interactivity API: Functions and hooks
+ *
+ * @package WordPress
+ * @subpackage Interactivity API
+ * @since 6.5.0
+ */
+
+/**
+ * Processes the directives on the rendered HTML of the interactive blocks.
+ *
+ * This processes only one root interactive block at a time because the
+ * rendered HTML of that block contains the rendered HTML of all its inner
+ * blocks, including any interactive block. It does so by ignoring all the
+ * interactive inner blocks until the root interactive block is processed.
+ *
+ * @since 6.5.0
+ *
+ * @param array $parsed_block The parsed block.
+ * @return array The same parsed block.
+ */
+function wp_interactivity_process_directives_of_interactive_blocks( array $parsed_block ): array {
+	static $root_interactive_block = null;
+
+	/*
+	 * Checks whether a root interactive block is already annotated for
+	 * processing, and if it is, it ignores the subsequent ones.
+	 */
+	if ( null === $root_interactive_block ) {
+		$block_name = $parsed_block['blockName'];
+		$block_type = WP_Block_Type_Registry::get_instance()->get_registered( $block_name );
+
+		if (
+			isset( $block_name ) &&
+			( ( isset( $block_type->supports['interactivity'] ) && true === $block_type->supports['interactivity'] ) ||
+			( isset( $block_type->supports['interactivity']['interactive'] ) && true === $block_type->supports['interactivity']['interactive'] ) )
+		) {
+			// Annotates the root interactive block for processing.
+			$root_interactive_block = array( $block_name, $parsed_block );
+
+			/*
+			 * Adds a filter to process the root interactive block once it has
+			 * finished rendering.
+			 */
+			$process_interactive_blocks = static function ( string $content, array $parsed_block ) use ( &$root_interactive_block, &$process_interactive_blocks ): string {
+				// Checks whether the current block is the root interactive block.
+				list($root_block_name, $root_parsed_block) = $root_interactive_block;
+				if ( $root_block_name === $parsed_block['blockName'] && $parsed_block === $root_parsed_block ) {
+					// The root interactive blocks has finished rendering, process it.
+					$content = wp_interactivity_process_directives( $content );
+					// Removes the filter and reset the root interactive block.
+					remove_filter( 'render_block_' . $parsed_block['blockName'], $process_interactive_blocks );
+					$root_interactive_block = null;
+				}
+				return $content;
+			};
+
+			/*
+			 * Uses a priority of 20 to ensure that other filters can add additional
+			 * directives before the processing starts.
+			 */
+			add_filter( 'render_block_' . $block_name, $process_interactive_blocks, 20, 2 );
+		}
+	}
+
+	return $parsed_block;
+}
+add_filter( 'render_block_data', 'wp_interactivity_process_directives_of_interactive_blocks' );
+
+/**
+ * Retrieves the main WP_Interactivity_API instance.
+ *
+ * It provides access to the WP_Interactivity_API instance, creating one if it
+ * doesn't exist yet.
+ *
+ * @global WP_Interactivity_API $wp_interactivity
+ *
+ * @since 6.5.0
+ *
+ * @return WP_Interactivity_API The main WP_Interactivity_API instance.
+ */
+function wp_interactivity(): WP_Interactivity_API {
+	global $wp_interactivity;
+	if ( ! ( $wp_interactivity instanceof WP_Interactivity_API ) ) {
+		$wp_interactivity = new WP_Interactivity_API();
+	}
+	return $wp_interactivity;
+}
+
+/**
+ * Processes the interactivity directives contained within the HTML content
+ * and updates the markup accordingly.
+ *
+ * @since 6.5.0
+ *
+ * @param string $html The HTML content to process.
+ * @return string The processed HTML content. It returns the original content when the HTML contains unbalanced tags.
+ */
+function wp_interactivity_process_directives( string $html ): string {
+	return wp_interactivity()->process_directives( $html );
+}
+
+/**
+ * Gets and/or sets the initial state of an Interactivity API store for a
+ * given namespace.
+ *
+ * If state for that store namespace already exists, it merges the new
+ * provided state with the existing one.
+ *
+ * @since 6.5.0
+ *
+ * @param string $store_namespace The unique store namespace identifier.
+ * @param array  $state           Optional. The array that will be merged with the existing state for the specified
+ *                                store namespace.
+ * @return array The state for the specified store namespace. This will be the updated state if a $state argument was
+ *               provided.
+ */
+function wp_interactivity_state( string $store_namespace, array $state = array() ): array {
+	return wp_interactivity()->state( $store_namespace, $state );
+}
+
+/**
+ * Gets and/or sets the configuration of the Interactivity API for a given
+ * store namespace.
+ *
+ * If configuration for that store namespace exists, it merges the new
+ * provided configuration with the existing one.
+ *
+ * @since 6.5.0
+ *
+ * @param string $store_namespace The unique store namespace identifier.
+ * @param array  $config          Optional. The array that will be merged with the existing configuration for the
+ *                                specified store namespace.
+ * @return array The configuration for the specified store namespace. This will be the updated configuration if a
+ *               $config argument was provided.
+ */
+function wp_interactivity_config( string $store_namespace, array $config = array() ): array {
+	return wp_interactivity()->config( $store_namespace, $config );
+}
+
+/**
+ * Generates a `data-wp-context` directive attribute by encoding a context
+ * array.
+ *
+ * This helper function simplifies the creation of `data-wp-context` directives
+ * by providing a way to pass an array of data, which encodes into a JSON string
+ * safe for direct use as a HTML attribute value.
+ *
+ * Example:
+ *
+ *     <div <?php echo data_wp_context( array( 'isOpen' => true, 'count' => 0 ) ); ?>>
+ *
+ * @since 6.5.0
+ *
+ * @param array  $context         The array of context data to encode.
+ * @param string $store_namespace Optional. The unique store namespace identifier.
+ * @return string A complete `data-wp-context` directive with a JSON encoded value representing the context array and
+ *                the store namespace if specified.
+ */
+function data_wp_context( array $context, string $store_namespace = '' ): string {
+	return 'data-wp-context=\'' .
+		( $store_namespace ? $store_namespace . '::' : '' ) .
+		( empty( $context ) ? '{}' : wp_json_encode( $context, JSON_HEX_TAG | JSON_HEX_APOS | JSON_HEX_QUOT | JSON_HEX_AMP ) ) .
+		'\'';
+}
diff --git a/src/wp-settings.php b/src/wp-settings.php
index a80c661d52a65..541f1092a3d31 100644
--- a/src/wp-settings.php
+++ b/src/wp-settings.php
@@ -378,9 +378,12 @@
 require ABSPATH . WPINC . '/fonts.php';
 require ABSPATH . WPINC . '/class-wp-script-modules.php';
 require ABSPATH . WPINC . '/script-modules.php';
-require ABSPATH . WPINC . '/interactivity-api.php';
+require ABSPATH . WPINC . '/interactivity-api/class-wp-interactivity-api.php';
+require ABSPATH . WPINC . '/interactivity-api/class-wp-interactivity-api-directives-processor.php';
+require ABSPATH . WPINC . '/interactivity-api/interactivity-api.php';
 
 wp_script_modules()->add_hooks();
+wp_interactivity()->add_hooks();
 
 $GLOBALS['wp_embed'] = new WP_Embed();
 
diff --git a/tests/phpunit/tests/interactivity-api/interactivity-api.php b/tests/phpunit/tests/interactivity-api/interactivity-api.php
new file mode 100644
index 0000000000000..c98d74f415350
--- /dev/null
+++ b/tests/phpunit/tests/interactivity-api/interactivity-api.php
@@ -0,0 +1,393 @@
+<?php
+/**
+ * Unit tests covering the functionality of the public functions of the
+ * Interactivity API.
+ *
+ * @package WordPress
+ * @subpackage Interactivity API
+ *
+ * @since 6.5.0
+ *
+ * @group interactivity-api
+ */
+class Tests_Interactivity_API_Functions extends WP_UnitTestCase {
+	/**
+	 * Set up.
+	 */
+	public function set_up() {
+		parent::set_up();
+
+		$interactive_block = array(
+			'render_callback' => function ( $attributes, $content ) {
+				return '
+						<div
+							data-wp-interactive=\'{ "namespace": "myPlugin" }\'
+							data-wp-context=\'{ "block": ' . $attributes['block'] . ' }\'
+						>
+							<input
+								class="interactive/block-' . $attributes['block'] . '"
+								data-wp-bind--value="context.block"
+							>' .
+						$content .
+					'</div>';
+			},
+			'supports'        => array(
+				'interactivity' => true,
+			),
+		);
+
+		register_block_type( 'test/interactive-block', $interactive_block );
+		register_block_type( 'test/interactive-block-2', $interactive_block );
+
+		register_block_type(
+			'test/non-interactive-block',
+			array(
+				'render_callback' => function ( $attributes, $content ) {
+					$directive = isset( $attributes['hasDirective'] ) ? ' data-wp-bind--value="context.block"' : '';
+					return '
+						<div>
+							<input class="non-interactive/block-' . $attributes['block'] . '"' . $directive . '>' .
+							$content .
+						'</div>';
+				},
+			)
+		);
+	}
+
+	/**
+	 * Tear down.
+	 */
+	public function tear_down() {
+		unregister_block_type( 'test/interactive-block' );
+		unregister_block_type( 'test/interactive-block-2' );
+		unregister_block_type( 'test/non-interactive-block' );
+		parent::tear_down();
+	}
+
+	/**
+	 * Tests processing of a single interactive block.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::wp_interactivity_process_directives_of_interactive_blocks
+	 */
+	public function test_processs_directives_of_single_interactive_block() {
+		$post_content    = '<!-- wp:test/interactive-block { "block": 1 } /-->';
+		$rendered_blocks = do_blocks( $post_content );
+		$p               = new WP_HTML_Tag_Processor( $rendered_blocks );
+		$p->next_tag( array( 'class_name' => 'interactive/block-1' ) );
+		$this->assertEquals( '1', $p->get_attribute( 'value' ) );
+	}
+
+	/**
+	 * Tests processing of multiple interactive blocks in parallel along with a
+	 * non-interactive block.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::wp_interactivity_process_directives_of_interactive_blocks
+	 */
+	public function test_processs_directives_of_multiple_interactive_blocks_in_paralell() {
+		$post_content    = '
+			<!-- wp:test/interactive-block { "block": 1 } /-->
+			<!-- wp:test/interactive-block-2 { "block": 2 } /-->
+			<!-- wp:test/non-interactive-block { "block": 3, "hasDirective": true } /-->
+			<!-- wp:test/interactive-block { "block": 4 } /-->
+		';
+		$rendered_blocks = do_blocks( $post_content );
+		$p               = new WP_HTML_Tag_Processor( $rendered_blocks );
+		$p->next_tag( array( 'class_name' => 'interactive/block-1' ) );
+		$this->assertEquals( '1', $p->get_attribute( 'value' ) );
+		$p->next_tag( array( 'class_name' => 'interactive/block-2' ) );
+		$this->assertEquals( '2', $p->get_attribute( 'value' ) );
+		$p->next_tag( array( 'class_name' => 'non-interactive/block-3' ) );
+		$this->assertNull( $p->get_attribute( 'value' ) );
+		$p->next_tag( array( 'class_name' => 'interactive/block-4' ) );
+		$this->assertEquals( '4', $p->get_attribute( 'value' ) );
+	}
+
+	/**
+	 * Tests processing of an interactive block inside a non-interactive block.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::wp_interactivity_process_directives_of_interactive_blocks
+	 */
+	public function test_processs_directives_of_interactive_block_inside_non_interactive_block() {
+		$post_content    = '
+			<!-- wp:test/non-interactive-block { "block": 1 } -->
+				<!-- wp:test/interactive-block { "block": 2 } /-->
+			<!-- /wp:test/non-interactive-block -->
+		';
+		$rendered_blocks = do_blocks( $post_content );
+		$p               = new WP_HTML_Tag_Processor( $rendered_blocks );
+		$p->next_tag( array( 'class_name' => 'interactive/block-2' ) );
+		$this->assertEquals( '2', $p->get_attribute( 'value' ) );
+	}
+
+	/**
+	 * Tests processing of multiple interactive blocks nested inside a
+	 * non-interactive block.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::wp_interactivity_process_directives_of_interactive_blocks
+	 */
+	public function test_processs_directives_of_multple_interactive_blocks_inside_non_interactive_block() {
+		$post_content    = '
+			<!-- wp:test/non-interactive-block { "block": 1 } -->
+				<!-- wp:test/interactive-block { "block": 2 } /-->
+				<!-- wp:test/interactive-block { "block": 3 } /-->
+			<!-- /wp:test/non-interactive-block -->
+		';
+		$rendered_blocks = do_blocks( $post_content );
+		$p               = new WP_HTML_Tag_Processor( $rendered_blocks );
+		$p->next_tag( array( 'class_name' => 'interactive/block-2' ) );
+		$this->assertEquals( '2', $p->get_attribute( 'value' ) );
+		$p->next_tag( array( 'class_name' => 'interactive/block-3' ) );
+		$this->assertEquals( '3', $p->get_attribute( 'value' ) );
+	}
+
+	/**
+	 * Tests processing of a single interactive block directive nested inside
+	 * multiple non-interactive blocks.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::wp_interactivity_process_directives_of_interactive_blocks
+	 */
+	public function test_processs_directives_of_interactive_block_inside_multple_non_interactive_block() {
+		$post_content    = '
+			<!-- wp:test/non-interactive-block { "block": 1 } -->
+				<!-- wp:test/interactive-block { "block": 2 } /-->
+			<!-- /wp:test/non-interactive-block -->
+			<!-- wp:test/non-interactive-block { "block": 3 } -->
+				<!-- wp:test/interactive-block-2 { "block": 4 } /-->
+			<!-- /wp:test/non-interactive-block -->
+		';
+		$rendered_blocks = do_blocks( $post_content );
+		$p               = new WP_HTML_Tag_Processor( $rendered_blocks );
+		$p->next_tag( array( 'class_name' => 'interactive/block-2' ) );
+		$this->assertEquals( '2', $p->get_attribute( 'value' ) );
+		$p->next_tag( array( 'class_name' => 'interactive/block-4' ) );
+		$this->assertEquals( '4', $p->get_attribute( 'value' ) );
+	}
+
+	/**
+	 * Tests processing of directives for an interactive block containing a
+	 * non-interactive block without directives.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::wp_interactivity_process_directives_of_interactive_blocks
+	 */
+	public function test_processs_directives_of_interactive_block_containing_non_interactive_block_without_directives() {
+		$post_content    = '
+			<!-- wp:test/interactive-block { "block": 1 } -->
+				<!-- wp:test/non-interactive-block { "block": 2 } /-->
+			<!-- /wp:test/interactive-block -->
+		';
+		$rendered_blocks = do_blocks( $post_content );
+		$p               = new WP_HTML_Tag_Processor( $rendered_blocks );
+		$p->next_tag( array( 'class_name' => 'interactive/block-1' ) );
+		$this->assertEquals( '1', $p->get_attribute( 'value' ) );
+		$p->next_tag( array( 'class_name' => 'non-interactive/block-2' ) );
+		$this->assertNull( $p->get_attribute( 'value' ) );
+	}
+
+	/**
+	 * Tests processing of directives for an interactive block containing a
+	 * non-interactive block with directives.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::wp_interactivity_process_directives_of_interactive_blocks
+	 */
+	public function test_processs_directives_of_interactive_block_containing_non_interactive_block_with_directives() {
+		$post_content    = '
+			<!-- wp:test/interactive-block { "block": 1 } -->
+				<!-- wp:test/non-interactive-block { "block": 2, "hasDirective": true } /-->
+			<!-- /wp:test/interactive-block -->
+		';
+		$rendered_blocks = do_blocks( $post_content );
+		$p               = new WP_HTML_Tag_Processor( $rendered_blocks );
+		$p->next_tag( array( 'class_name' => 'interactive/block-1' ) );
+		$this->assertEquals( '1', $p->get_attribute( 'value' ) );
+		$p->next_tag( array( 'class_name' => 'non-interactive/block-2' ) );
+		$this->assertEquals( '1', $p->get_attribute( 'value' ) );
+	}
+
+	/**
+	 * Tests processing of directives for an interactive block containing nested
+	 * interactive and non-interactive blocks, checking proper propagation of
+	 * context.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::wp_interactivity_process_directives_of_interactive_blocks
+	 */
+	public function test_processs_directives_of_interactive_block_containing_nested_interactive_and_non_interactive_blocks() {
+		$post_content    = '
+			<!-- wp:test/interactive-block { "block": 1 } -->
+				<!-- wp:test/interactive-block-2 { "block": 2 } -->
+					<!-- wp:test/non-interactive-block { "block": 3, "hasDirective": true } /-->
+				<!-- /wp:test/interactive-block-2 -->
+				<!-- wp:test/non-interactive-block { "block": 4, "hasDirective": true } /-->
+			<!-- /wp:test/interactive-block -->
+		';
+		$rendered_blocks = do_blocks( $post_content );
+		$p               = new WP_HTML_Tag_Processor( $rendered_blocks );
+		$p->next_tag( array( 'class_name' => 'interactive/block-1' ) );
+		$this->assertEquals( '1', $p->get_attribute( 'value' ) );
+		$p->next_tag( array( 'class_name' => 'interactive/block-2' ) );
+		$this->assertEquals( '2', $p->get_attribute( 'value' ) );
+		$p->next_tag( array( 'class_name' => 'non-interactive/block-3' ) );
+		$this->assertEquals( '2', $p->get_attribute( 'value' ) );
+		$p->next_tag( array( 'class_name' => 'non-interactive/block-4' ) );
+		$this->assertEquals( '1', $p->get_attribute( 'value' ) );
+	}
+
+	/**
+	 * Counter for the number of times the test directive processor is called.
+	 *
+	 * @var int
+	 */
+	private $data_wp_test_processor_count = 0;
+
+	/**
+	 * Test directive processor callback.
+	 *
+	 * Increments the $data_wp_test_processor_count every time a tag that is not a
+	 * tag closer is processed.
+	 *
+	 * @param WP_HTML_Tag_Processor $p Instance of the processor handling the current HTML tag.
+	 */
+	public function data_wp_test_processor( $p ) {
+		if ( ! $p->is_tag_closer() ) {
+			$this->data_wp_test_processor_count = $this->data_wp_test_processor_count + 1;
+		}
+	}
+
+	/**
+	 * Tests that directives are only processed once for the root interactive
+	 * blocks.
+	 *
+	 * This ensures that nested blocks do not trigger additional processing of the
+	 * same directives, leading to incorrect behavior or performance issues.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::wp_interactivity_process_directives_of_interactive_blocks
+	 */
+	public function test_process_directives_only_process_the_root_interactive_blocks() {
+		$class                = new ReflectionClass( 'WP_Interactivity_API' );
+		$directive_processors = $class->getProperty( 'directive_processors' );
+		$directive_processors->setAccessible( true );
+		$old_directive_processors = $directive_processors->getValue();
+		$directive_processors->setValue( null, array( 'data-wp-test' => array( $this, 'data_wp_test_processor' ) ) );
+		$html                               = '<div data-wp-test></div>';
+		$this->data_wp_test_processor_count = 0;
+		wp_interactivity_process_directives( $html );
+		$this->assertEquals( 1, $this->data_wp_test_processor_count );
+
+		register_block_type(
+			'test/custom-directive-block',
+			array(
+				'render_callback' => function ( $attributes, $content ) {
+					return '<div class="test" data-wp-test>' . $content . '</div>';
+				},
+				'supports'        => array(
+					'interactivity' => true,
+				),
+			)
+		);
+		$post_content                       = '
+			<!-- wp:test/custom-directive-block -->
+				<!-- wp:test/custom-directive-block /-->
+			<!-- /wp:test/custom-directive-block -->
+		';
+		$this->data_wp_test_processor_count = 0;
+		do_blocks( $post_content );
+		$this->assertEquals( 2, $this->data_wp_test_processor_count );
+		unregister_block_type( 'test/custom-directive-block' );
+		$directive_processors->setValue( null, $old_directive_processors );
+	}
+
+	/**
+	 * Tests that data_wp_context function correctly converts different array
+	 * structures to a JSON string.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::data_wp_context
+	 */
+	public function test_data_wp_context_with_different_arrays() {
+		$this->assertEquals( 'data-wp-context=\'{}\'', data_wp_context( array() ) );
+		$this->assertEquals(
+			'data-wp-context=\'{"a":1,"b":"2","c":true}\'',
+			data_wp_context(
+				array(
+					'a' => 1,
+					'b' => '2',
+					'c' => true,
+				)
+			)
+		);
+		$this->assertEquals(
+			'data-wp-context=\'{"a":[1,2]}\'',
+			data_wp_context( array( 'a' => array( 1, 2 ) ) )
+		);
+		$this->assertEquals(
+			'data-wp-context=\'[1,2]\'',
+			data_wp_context( array( 1, 2 ) )
+		);
+	}
+
+	/**
+	 * Tests that data_wp_context function correctly converts different array
+	 * structures to a JSON string and adds a namespace.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::data_wp_context
+	 */
+	public function test_data_wp_context_with_different_arrays_and_a_namespace() {
+		$this->assertEquals( 'data-wp-context=\'myPlugin::{}\'', data_wp_context( array(), 'myPlugin' ) );
+		$this->assertEquals(
+			'data-wp-context=\'myPlugin::{"a":1,"b":"2","c":true}\'',
+			data_wp_context(
+				array(
+					'a' => 1,
+					'b' => '2',
+					'c' => true,
+				),
+				'myPlugin'
+			)
+		);
+		$this->assertEquals(
+			'data-wp-context=\'myPlugin::{"a":[1,2]}\'',
+			data_wp_context( array( 'a' => array( 1, 2 ) ), 'myPlugin' )
+		);
+		$this->assertEquals(
+			'data-wp-context=\'myPlugin::[1,2]\'',
+			data_wp_context( array( 1, 2 ), 'myPlugin' )
+		);
+	}
+
+	/**
+	 * Tests that data_wp_context function correctly applies the JSON encoding
+	 * flags. This ensures that characters like `<`, `>`, `'`, or `&` are
+	 * properly escaped in the JSON-encoded string to prevent potential XSS
+	 * attacks.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::data_wp_context
+	 */
+	public function test_data_wp_context_with_json_flags() {
+		$this->assertEquals( 'data-wp-context=\'{"tag":"\u003Cfoo\u003E"}\'', data_wp_context( array( 'tag' => '<foo>' ) ) );
+		$this->assertEquals( 'data-wp-context=\'{"apos":"\u0027bar\u0027"}\'', data_wp_context( array( 'apos' => "'bar'" ) ) );
+		$this->assertEquals( 'data-wp-context=\'{"quot":"\u0022baz\u0022"}\'', data_wp_context( array( 'quot' => '"baz"' ) ) );
+		$this->assertEquals( 'data-wp-context=\'{"amp":"T\u0026T"}\'', data_wp_context( array( 'amp' => 'T&T' ) ) );
+	}
+}
diff --git a/tests/phpunit/tests/interactivity-api/wpInteractivityAPI-wp-bind.php b/tests/phpunit/tests/interactivity-api/wpInteractivityAPI-wp-bind.php
new file mode 100644
index 0000000000000..2c530e4faf817
--- /dev/null
+++ b/tests/phpunit/tests/interactivity-api/wpInteractivityAPI-wp-bind.php
@@ -0,0 +1,382 @@
+<?php
+/**
+ * Unit tests covering the data_wp_bind_processor functionality of the
+ * WP_Interactivity_API class.
+ *
+ * @package WordPress
+ * @subpackage Interactivity API
+ *
+ * @since 6.5.0
+ *
+ * @group interactivity-api
+ */
+class Tests_WP_Interactivity_API_WP_Bind extends WP_UnitTestCase {
+	/**
+	 * Instance of WP_Interactivity_API.
+	 *
+	 * @var WP_Interactivity_API
+	 */
+	protected $interactivity;
+
+	/**
+	 * Set up.
+	 */
+	public function set_up() {
+		parent::set_up();
+		$this->interactivity = new WP_Interactivity_API();
+		$this->interactivity->state(
+			'myPlugin',
+			array(
+				'id'          => 'some-id',
+				'width'       => 100,
+				'isOpen'      => false,
+				'null'        => null,
+				'trueString'  => 'true',
+				'falseString' => 'false',
+			)
+		);
+	}
+
+	/**
+	 * Invokes the `process_directives` method of WP_Interactivity_API class.
+	 *
+	 * @param string $html The HTML that needs to be processed.
+	 * @return array An array containing an instance of the WP_HTML_Tag_Processor and the processed HTML.
+	 */
+	private function process_directives( $html ) {
+		$new_html = $this->interactivity->process_directives( $html );
+		$p        = new WP_HTML_Tag_Processor( $new_html );
+		$p->next_tag();
+		return array( $p, $new_html );
+	}
+
+	/**
+	 * Tests setting an attribute via `data-wp-bind`.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_bind_sets_attribute() {
+		$html    = '<div data-wp-bind--id="myPlugin::state.id">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-id', $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests replacing an existing attribute via `data-wp-bind`.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_bind_replaces_attribute() {
+		$html    = '<div id="other-id" data-wp-bind--id="myPlugin::state.id">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-id', $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests setting a numerical value as an attribute via `data-wp-bind`.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_bind_sets_number_value() {
+		$html    = '<img data-wp-bind--width="myPlugin::state.width">';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( '100', $p->get_attribute( 'width' ) );
+	}
+
+	/**
+	 * Tests that true strings are set properly as attribute values.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_bind_sets_true_string() {
+		$html               = '<div data-wp-bind--id="myPlugin::state.trueString">Text</div>';
+		list($p, $new_html) = $this->process_directives( $html );
+		$this->assertEquals( 'true', $p->get_attribute( 'id' ) );
+		$this->assertEquals( '<div id="true" data-wp-bind--id="myPlugin::state.trueString">Text</div>', $new_html );
+	}
+
+	/**
+	 * Tests that false strings are set properly as attribute values.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_bind_sets_false_string() {
+		$html               = '<div data-wp-bind--id="myPlugin::state.falseString">Text</div>';
+		list($p, $new_html) = $this->process_directives( $html );
+		$this->assertEquals( 'false', $p->get_attribute( 'id' ) );
+		$this->assertEquals( '<div id="false" data-wp-bind--id="myPlugin::state.falseString">Text</div>', $new_html );
+	}
+
+	/**
+	 * Tests that `data-wp-bind` ignores directives with no suffix.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_bind_ignores_empty_bound_attribute() {
+		$html     = '<div data-wp-bind="myPlugin::state.id">Text</div>';
+		$new_html = $this->interactivity->process_directives( $html );
+		$this->assertEquals( $html, $new_html );
+	}
+
+	/**
+	 * Tests that `data-wp-bind` does nothing when referencing non-existent
+	 * references.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_bind_doesnt_do_anything_on_non_existent_references() {
+		$html     = '<div data-wp-bind--id="myPlugin::state.nonExistengKey">Text</div>';
+		$new_html = $this->interactivity->process_directives( $html );
+		$this->assertEquals( $html, $new_html );
+	}
+
+	/**
+	 * Tests that `data-wp-bind` ignores directives with empty values.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_bind_ignores_empty_value() {
+		$html     = '<div data-wp-bind--id="">Text</div>';
+		$new_html = $this->interactivity->process_directives( $html );
+		$this->assertEquals( $html, $new_html );
+	}
+
+	/**
+	 * Tests that `data-wp-bind` ignores directives without values.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_bind_ignores_without_value() {
+		$html     = '<div data-wp-bind--id>Text</div>';
+		$new_html = $this->interactivity->process_directives( $html );
+		$this->assertEquals( $html, $new_html );
+	}
+
+	/**
+	 * Tests that `data-wp-bind` works with multiple instances of the same
+	 * directive on a tag.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_bind_works_with_multiple_same_directives() {
+		$html    = '<div data-wp-bind--id="myPlugin::state.id" data-wp-bind--id="myPlugin::state.id">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-id', $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that `data-wp-bind` works with multiple instances of different
+	 * directives on a tag.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_bind_works_with_multiple_different_directives() {
+		$html    = '<img data-wp-bind--id="myPlugin::state.id" data-wp-bind--width="myPlugin::state.width">';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-id', $p->get_attribute( 'id' ) );
+		$this->assertEquals( '100', $p->get_attribute( 'width' ) );
+	}
+
+	/**
+	 * Tests adding boolean attributes to a tag using `data-wp-bind`.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_bind_adds_boolean_attribute_if_true() {
+		$html               = '<div data-wp-bind--hidden="myPlugin::!state.isOpen">Text</div>';
+		list($p, $new_html) = $this->process_directives( $html );
+		$this->assertTrue( $p->get_attribute( 'hidden' ) );
+		$this->assertEquals( '<div hidden data-wp-bind--hidden="myPlugin::!state.isOpen">Text</div>', $new_html );
+	}
+
+	/**
+	 * Tests replacing a pre-existing boolean attribute on a tag using
+	 * `data-wp-bind`.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_bind_replaces_existing_attribute_if_true() {
+		$html               = '<div hidden="true" data-wp-bind--hidden="myPlugin::!state.isOpen">Text</div>';
+		list($p, $new_html) = $this->process_directives( $html );
+		$this->assertTrue( $p->get_attribute( 'hidden' ) );
+		$this->assertEquals( '<div hidden data-wp-bind--hidden="myPlugin::!state.isOpen">Text</div>', $new_html );
+	}
+
+	/**
+	 * Tests that boolean attributes are not added when bound to false or null
+	 * values.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_bind_doesnt_add_boolean_attribute_if_false_or_null() {
+		$html               = '<div data-wp-bind--hidden="myPlugin::state.isOpen">Text</div>';
+		list($p, $new_html) = $this->process_directives( $html );
+		$this->assertNull( $p->get_attribute( 'hidden' ) );
+		$this->assertEquals( $html, $new_html );
+
+		$html               = '<div data-wp-bind--hidden="myPlugin::state.null">Text</div>';
+		list($p, $new_html) = $this->process_directives( $html );
+		$this->assertNull( $p->get_attribute( 'hidden' ) );
+		$this->assertEquals( $html, $new_html );
+	}
+
+	/**
+	 * Tests removing boolean attributes from a tag using `data-wp-bind` and a
+	 * false or null value.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_bind_removes_boolean_attribute_if_false_or_null() {
+		$html    = '<div hidden data-wp-bind--hidden="myPlugin::state.isOpen">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertNull( $p->get_attribute( 'hidden' ) );
+
+		$html    = '<div hidden data-wp-bind--hidden="myPlugin::state.null">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertNull( $p->get_attribute( 'hidden' ) );
+	}
+
+	/**
+	 * Tests adding values to aria or data attributes when the condition evaluates
+	 * to true.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_bind_adds_value_if_true_in_aria_or_data_attributes() {
+		$html               = '<div data-wp-bind--aria-hidden="myPlugin::!state.isOpen">Text</div>';
+		list($p, $new_html) = $this->process_directives( $html );
+		$this->assertEquals( 'true', $p->get_attribute( 'aria-hidden' ) );
+		$this->assertEquals( '<div aria-hidden="true" data-wp-bind--aria-hidden="myPlugin::!state.isOpen">Text</div>', $new_html );
+
+		$html               = '<div data-wp-bind--data-is-closed="myPlugin::!state.isOpen">Text</div>';
+		list($p, $new_html) = $this->process_directives( $html );
+		$this->assertEquals( 'true', $p->get_attribute( 'data-is-closed' ) );
+		$this->assertEquals( '<div data-is-closed="true" data-wp-bind--data-is-closed="myPlugin::!state.isOpen">Text</div>', $new_html );
+	}
+
+	/**
+	 * Tests replacing values in aria or data attributes when the condition
+	 * evaluates to true.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_bind_replaces_value_if_true_in_aria_or_data_attributes() {
+		$html               = '<div aria-hidden="false" data-wp-bind--aria-hidden="myPlugin::!state.isOpen">Text</div>';
+		list($p, $new_html) = $this->process_directives( $html );
+		$this->assertEquals( 'true', $p->get_attribute( 'aria-hidden' ) );
+		$this->assertEquals( '<div aria-hidden="true" data-wp-bind--aria-hidden="myPlugin::!state.isOpen">Text</div>', $new_html );
+
+		$html     = '<div data-is-closed="false" data-wp-bind--data-is-closed="myPlugin::!state.isOpen">Text</div>';
+		$new_html = $this->interactivity->process_directives( $html );
+		$p        = new WP_HTML_Tag_Processor( $new_html );
+		$p->next_tag();
+		$this->assertEquals( 'true', $p->get_attribute( 'data-is-closed' ) );
+		$this->assertEquals( '<div data-is-closed="true" data-wp-bind--data-is-closed="myPlugin::!state.isOpen">Text</div>', $new_html );
+	}
+
+	/**
+	 * Tests adding the value 'false' to aria or data attributes when the
+	 * condition evaluates to false.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_bind_adds_value_if_false_in_aria_or_data_attributes() {
+		$html               = '<div data-wp-bind--aria-hidden="myPlugin::state.isOpen">Text</div>';
+		list($p, $new_html) = $this->process_directives( $html );
+		$this->assertEquals( 'false', $p->get_attribute( 'aria-hidden' ) );
+		$this->assertEquals( '<div aria-hidden="false" data-wp-bind--aria-hidden="myPlugin::state.isOpen">Text</div>', $new_html );
+
+		$html               = '<div data-wp-bind--data-is-closed="myPlugin::state.isOpen">Text</div>';
+		list($p, $new_html) = $this->process_directives( $html );
+		$this->assertEquals( 'false', $p->get_attribute( 'data-is-closed' ) );
+		$this->assertEquals( '<div data-is-closed="false" data-wp-bind--data-is-closed="myPlugin::state.isOpen">Text</div>', $new_html );
+	}
+
+	/**
+	 * Tests replacing values in aria or data attributes when the condition
+	 * evaluates to false.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_bind_replaces_value_if_false_in_aria_or_data_attributes() {
+		$html               = '<div aria-hidden="true" data-wp-bind--aria-hidden="myPlugin::state.isOpen">Text</div>';
+		list($p, $new_html) = $this->process_directives( $html );
+		$this->assertEquals( 'false', $p->get_attribute( 'aria-hidden' ) );
+		$this->assertEquals( '<div aria-hidden="false" data-wp-bind--aria-hidden="myPlugin::state.isOpen">Text</div>', $new_html );
+
+		$html               = '<div data-is-closed="true" data-wp-bind--data-is-closed="myPlugin::state.isOpen">Text</div>';
+		list($p, $new_html) = $this->process_directives( $html );
+		$this->assertEquals( 'false', $p->get_attribute( 'data-is-closed' ) );
+		$this->assertEquals( '<div data-is-closed="false" data-wp-bind--data-is-closed="myPlugin::state.isOpen">Text</div>', $new_html );
+	}
+
+	/**
+	 * Tests removing values from aria or data attributes when the value is null.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_bind_removes_value_if_null_in_aria_or_data_attributes() {
+		$html    = '<div aria-hidden="true" data-wp-bind--aria-hidden="myPlugin::state.null">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertNull( $p->get_attribute( 'aria-hidden' ) );
+
+		$html    = '<div data-is-closed="true" data-wp-bind--data-is-closed="myPlugin::state.null">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertNull( $p->get_attribute( 'data-is-closed' ) );
+	}
+
+	/**
+	 * Tests handling of bindings within nested tags.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_bind_handles_nested_bindings() {
+		$html    = '<div data-wp-bind--id="myPlugin::state.id"><img data-wp-bind--width="myPlugin::state.width"></div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-id', $p->get_attribute( 'id' ) );
+		$p->next_tag();
+		$this->assertEquals( '100', $p->get_attribute( 'width' ) );
+	}
+}
diff --git a/tests/phpunit/tests/interactivity-api/wpInteractivityAPI-wp-class.php b/tests/phpunit/tests/interactivity-api/wpInteractivityAPI-wp-class.php
new file mode 100644
index 0000000000000..54c9ee5af5e42
--- /dev/null
+++ b/tests/phpunit/tests/interactivity-api/wpInteractivityAPI-wp-class.php
@@ -0,0 +1,327 @@
+<?php
+/**
+ * Unit tests covering the data_wp_class_processor functionality of the
+ * WP_Interactivity_API class.
+ *
+ * @package WordPress
+ * @subpackage Interactivity API
+ *
+ * @since 6.5.0
+ *
+ * @group interactivity-api
+ */
+class Tests_WP_Interactivity_API_WP_Class extends WP_UnitTestCase {
+	/**
+	 * Instance of WP_Interactivity_API.
+	 *
+	 * @var WP_Interactivity_API
+	 */
+	protected $interactivity;
+
+	/**
+	 * Set up.
+	 */
+	public function set_up() {
+		parent::set_up();
+		$this->interactivity = new WP_Interactivity_API();
+		$this->interactivity->state(
+			'myPlugin',
+			array(
+				'true'  => true,
+				'false' => false,
+			)
+		);
+	}
+
+	/**
+	 * Invokes the `process_directives` method of WP_Interactivity_API class.
+	 *
+	 * @param string $html The HTML that needs to be processed.
+	 * @return array An array containing an instance of the WP_HTML_Tag_Processor and the processed HTML.
+	 */
+	private function process_directives( $html ) {
+		$new_html = $this->interactivity->process_directives( $html );
+		$p        = new WP_HTML_Tag_Processor( $new_html );
+		$p->next_tag();
+		return array( $p, $new_html );
+	}
+
+	/**
+	 * Tests that `data-wp-class` adds a class when the condition is true.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_class_sets_class_name() {
+		$html    = '<div data-wp-class--some-class="myPlugin::state.true">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-class', $p->get_attribute( 'class' ) );
+	}
+
+	/**
+	 * Tests that `data-wp-class` can add multiple classes based on true
+	 * conditions.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_class_sets_multiple_class_names() {
+		$html    = '
+			<div
+				data-wp-class--some-class="myPlugin::state.true"
+				data-wp-class--other-class="myPlugin::state.true"
+			>Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-class other-class', $p->get_attribute( 'class' ) );
+	}
+
+	/**
+	 * Tests handling of adding one and not adding another class based on
+	 * different boolean values.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_class_handles_multiple_class_names_with_different_values() {
+		$html    = '
+			<div
+				data-wp-class--some-class="myPlugin::state.true"
+				data-wp-class--other-class="myPlugin::state.false"
+			>Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-class', $p->get_attribute( 'class' ) );
+
+		$html    = '
+			<div
+				class="other-class"
+				data-wp-class--some-class="myPlugin::state.true"
+				data-wp-class--other-class="myPlugin::state.false"
+			>Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-class', $p->get_attribute( 'class' ) );
+	}
+
+	/**
+	 * Tests that `data-wp-class` adds new classes alongside existing ones.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_class_sets_class_name_when_class_attribute_exists() {
+		$html    = '<div class="other-class" data-wp-class--some-class="myPlugin::state.true">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'other-class some-class', $p->get_attribute( 'class' ) );
+	}
+
+	/**
+	 * Tests that no class is added when the associated state is false.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_class_doesnt_add_class_attribute_on_false() {
+		$html    = '<div data-wp-class--some-class="myPlugin::state.false">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertNull( $p->get_attribute( 'class' ) );
+	}
+
+	/**
+	 * Tests that existing class names are preserved when the directive condition
+	 * is false.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_class_doesnt_add_class_name_on_false() {
+		$html    = '<div class="other-class" data-wp-class--some-class="myPlugin::state.false">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'other-class', $p->get_attribute( 'class' ) );
+	}
+
+	/**
+	 * Tests that existing class names remain intact when they should be re-added
+	 * as per their directive.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_class_keeps_class_name_when_class_name_exists() {
+		$html    = '<div class="some-class" data-wp-class--some-class="myPlugin::state.true">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-class', $p->get_attribute( 'class' ) );
+	}
+
+	/**
+	 * Tests preservation of existing class names, even when one is repeated in a
+	 * directive that evaluates to true.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_class_keeps_class_name_when_class_name_exists_and_is_not_the_only_one() {
+		$html    = '<div class="other-class some-class" data-wp-class--some-class="myPlugin::state.true">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'other-class some-class', $p->get_attribute( 'class' ) );
+	}
+
+	/**
+	 * Tests that a class attribute with only one class name is removed when the
+	 * directive evaluates to false.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_class_removes_class_attribute_when_class_name_exists_and_is_the_only_one() {
+		$html    = '<div class="some-class" data-wp-class--some-class="myPlugin::state.false">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertNull( $p->get_attribute( 'class' ) );
+	}
+
+	/**
+	 * Tests that one of several class names is removed when its directive
+	 * evaluates to false.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_class_removes_class_name_when_class_name_exists_and_is_not_the_only_one() {
+		$html    = '<div class="other-class some-class" data-wp-class--some-class="myPlugin::state.false">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'other-class', $p->get_attribute( 'class' ) );
+	}
+
+	/**
+	 * Tests that an empty class attribute is not removed even if a directive
+	 * evaluates to false.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_class_doesnt_remove_empty_class_attribute() {
+		$html    = '<div class data-wp-class--some-class="myPlugin::state.false">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertTrue( $p->get_attribute( 'class' ) );
+	}
+
+	/**
+	 * Tests that the class attribute remains unchanged if the data-wp-class
+	 * suffix is empty.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_class_doesnt_change_class_attribute_with_empty_directive_suffix() {
+		$html    = '<div class="other-class" data-wp-class="myPlugin::state.true">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'other-class', $p->get_attribute( 'class' ) );
+	}
+
+	/**
+	 * Tests that the class attribute is not altered if the value of the
+	 * `data-wp-class` directive is empty.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_class_doesnt_change_class_attribute_with_empty_value() {
+		$html    = '<div class="other-class" data-wp-class--some-class="">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'other-class', $p->get_attribute( 'class' ) );
+	}
+
+	/**
+	 * Tests that an existing class attribute is not affected by a `data-wp-class`
+	 * directive without a value.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_class_doesnt_change_class_attribute_without_value() {
+		$html    = '<div class="other-class" data-wp-class--some-class>Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'other-class', $p->get_attribute( 'class' ) );
+	}
+
+	/**
+	 * Tests that multiple directives for the same class yield the correct result
+	 * when the condition is true.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_class_works_with_multiple_directives() {
+		$html    = '<div data-wp-class--some-class="myPlugin::state.true" data-wp-class--some-class="myPlugin::state.true">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-class', $p->get_attribute( 'class' ) );
+	}
+
+	/**
+	 * Tests setting class names based on truthy values other than just true
+	 * booleans.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_class_sets_class_name_on_truthy_values() {
+		$this->interactivity->state( 'myPlugin', array( 'text' => 'some text' ) );
+		$html    = '<div data-wp-class--some-class="myPlugin::state.text">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-class', $p->get_attribute( 'class' ) );
+
+		$this->interactivity->state( 'myPlugin', array( 'array' => array( 1, 2 ) ) );
+		$html    = '<div data-wp-class--some-class="myPlugin::state.array">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-class', $p->get_attribute( 'class' ) );
+
+		$this->interactivity->state( 'myPlugin', array( 'number' => 1 ) );
+		$html    = '<div data-wp-class--some-class="myPlugin::state.number">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-class', $p->get_attribute( 'class' ) );
+	}
+
+	/**
+	 * Tests that class attributes aren't set for falsy values other than just
+	 * false booleans.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_class_sets_class_name_on_falsy_values() {
+		$this->interactivity->state( 'myPlugin', array( 'text' => '' ) );
+		$html    = '<div data-wp-class--some-class="myPlugin::state.text">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertNull( $p->get_attribute( 'class' ) );
+
+		$this->interactivity->state( 'myPlugin', array( 'array' => array() ) );
+		$html    = '<div data-wp-class--some-class="myPlugin::state.array">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertNull( $p->get_attribute( 'class' ) );
+
+		$this->interactivity->state( 'myPlugin', array( 'number' => 0 ) );
+		$html    = '<div data-wp-class--some-class="myPlugin::state.number">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertNull( $p->get_attribute( 'class' ) );
+
+		$this->interactivity->state( 'myPlugin', array( 'null' => null ) );
+		$html    = '<div data-wp-class--some-class="myPlugin::state.null">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertNull( $p->get_attribute( 'class' ) );
+	}
+}
diff --git a/tests/phpunit/tests/interactivity-api/wpInteractivityAPI-wp-context.php b/tests/phpunit/tests/interactivity-api/wpInteractivityAPI-wp-context.php
new file mode 100644
index 0000000000000..b56d38d05ec9b
--- /dev/null
+++ b/tests/phpunit/tests/interactivity-api/wpInteractivityAPI-wp-context.php
@@ -0,0 +1,522 @@
+<?php
+/**
+ * Unit tests covering the data_wp_context_processor functionality of the
+ * WP_Interactivity_API class.
+ *
+ * @package WordPress
+ * @subpackage Interactivity API
+ *
+ * @since 6.5.0
+ *
+ * @group interactivity-api
+ */
+class Tests_WP_Interactivity_API_WP_Context extends WP_UnitTestCase {
+	/**
+	 * Instance of WP_Interactivity_API.
+	 *
+	 * @var WP_Interactivity_API
+	 */
+	protected $interactivity;
+
+	/**
+	 * Set up.
+	 */
+	public function set_up() {
+		parent::set_up();
+		$this->interactivity = new WP_Interactivity_API();
+	}
+
+	/**
+	 * Invokes the `process_directives` method of WP_Interactivity_API class.
+	 *
+	 * @param string $html The HTML that needs to be processed.
+	 * @return array An array containing an instance of the WP_HTML_Tag_Processor and the processed HTML.
+	 */
+	private function process_directives( $html ) {
+		$new_html = $this->interactivity->process_directives( $html );
+		$p        = new WP_HTML_Tag_Processor( $new_html );
+		$p->next_tag( array( 'class_name' => 'test' ) );
+		return array( $p, $new_html );
+	}
+
+	/**
+	 * Tests that the `data-wp-context` directive can set a context in a custom
+	 * namespace.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_context_directive_sets_a_context_in_a_custom_namespace() {
+		$html    = '
+			<div data-wp-context=\'myPlugin::{ "id": "some-id" }\'>
+				<div class="test" data-wp-bind--id="myPlugin::context.id">Text</div>
+			</div>
+		';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-id', $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-context` directive can set a context in the same
+	 * tag.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_context_directive_can_set_a_context_in_the_same_tag() {
+		$html    = '
+			<div
+				class="test"
+				data-wp-context=\'myPlugin::{ "id": "some-id" }\'
+				data-wp-bind--id="myPlugin::context.id"
+			>
+				Text
+			</div>
+		';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-id', $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-context` directive merges context in the same
+	 * custom namespace.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_context_directive_merges_context_in_the_same_custom_namespace() {
+		$html    = '
+			<div data-wp-context=\'myPlugin::{ "id1": "some-id-1" }\'>
+				<div data-wp-context=\'myPlugin::{ "id2": "some-id-2" }\'>
+					<div class="test" data-wp-bind--id="myPlugin::context.id1">Text</div>
+					<div class="test" data-wp-bind--id="myPlugin::context.id2">Text</div>
+				</div>
+			</div>
+		';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-id-1', $p->get_attribute( 'id' ) );
+		$p->next_tag( array( 'class_name' => 'test' ) );
+		$this->assertEquals( 'some-id-2', $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-context` directive overwrites context in the same
+	 * custom namespace.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_context_directive_overwrites_context_in_the_same_custom_namespace() {
+		$html    = '
+			<div data-wp-context=\'myPlugin::{ "id": "some-id-1" }\'>
+				<div data-wp-context=\'myPlugin::{ "id": "some-id-2" }\'>
+					<div class="test" data-wp-bind--id="myPlugin::context.id">Text</div>
+				</div>
+			</div>
+		';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-id-2', $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-context` directive replaces the old context after a
+	 * closing tag in the same custom namespace.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_context_directive_replaces_old_context_after_closing_tag_in_the_same_custom_namespace() {
+		$html    = '
+			<div data-wp-context=\'myPlugin::{ "id": "some-id-1" }\'>
+				<div data-wp-context=\'myPlugin::{ "id": "some-id-2" }\'>
+					<div class="test" data-wp-bind--id="myPlugin::context.id">Text</div>
+				</div>
+				<div class="test" data-wp-bind--id="myPlugin::context.id">Text</div>
+			</div>
+		';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-id-2', $p->get_attribute( 'id' ) );
+		$p->next_tag( array( 'class_name' => 'test' ) );
+		$this->assertEquals( 'some-id-1', $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-context` directive merges context in different
+	 * custom namespaces.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_context_directive_merges_context_in_different_custom_namespaces() {
+		$html    = '
+			<div data-wp-context=\'myPlugin::{ "id": "some-id-1" }\'>
+				<div data-wp-context=\'otherPlugin::{ "id": "some-id-2" }\'>
+					<div class="test" data-wp-bind--id="myPlugin::context.id">Text</div>
+					<div class="test" data-wp-bind--id="otherPlugin::context.id">Text</div>
+				</div>
+			</div>
+		';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-id-1', $p->get_attribute( 'id' ) );
+		$p->next_tag( array( 'class_name' => 'test' ) );
+		$this->assertEquals( 'some-id-2', $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-context` directive doesn't throw on malformed
+	 * context objects.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_context_directive_doesnt_throw_on_malformed_context_objects() {
+		$html    = '
+			<div data-wp-context=\'myPlugin::{ id: "some-id" }\'>
+				<div class="test" data-wp-bind--id="myPlugin::context.id">Text</div>
+			</div>
+		';
+		list($p) = $this->process_directives( $html );
+		$this->assertNull( $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-context` directive doesn't overwrite context on
+	 * malformed context objects.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_context_directive_doesnt_overwrite_context_on_malformed_context_objects() {
+		$html    = '
+			<div data-wp-context=\'myPlugin::{ "id": "some-id-1" }\'>
+				<div data-wp-context=\'myPlugin::{ id: "some-id-2" }\'>
+					<div class="test" data-wp-bind--id="myPlugin::context.id">Text</div>
+				</div>
+				<div class="test" data-wp-bind--id="myPlugin::context.id">Text</div>
+			</div>
+		';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-id-1', $p->get_attribute( 'id' ) );
+		$p->next_tag( array( 'class_name' => 'test' ) );
+		$this->assertEquals( 'some-id-1', $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-context` directive doesn't throw on an empty
+	 * context object.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_context_directive_doesnt_throw_on_empty_context() {
+		$html    = '
+			<div data-wp-context="">
+				<div class="test" data-wp-bind--id="myPlugin::context.id">Text</div>
+			</div>
+		';
+		list($p) = $this->process_directives( $html );
+		$this->assertNull( $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-context` directive doesn't overwrite the context on
+	 * empty context directive.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_context_directive_doesnt_overwrite_context_on_empty_context() {
+		$html    = '
+			<div data-wp-context=\'myPlugin::{ "id": "some-id-1" }\'>
+				<div data-wp-context="">
+					<div class="test" data-wp-bind--id="myPlugin::context.id">Text</div>
+				</div>
+				<div class="test" data-wp-bind--id="myPlugin::context.id">Text</div>
+			</div>
+		';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-id-1', $p->get_attribute( 'id' ) );
+		$p->next_tag( array( 'class_name' => 'test' ) );
+		$this->assertEquals( 'some-id-1', $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-context` directive doesn't throw on context without
+	 * value.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_context_directive_doesnt_throw_on_context_without_value() {
+		$html    = '
+			<div data-wp-context>
+				<div class="test" data-wp-bind--id="myPlugin::context.id">Text</div>
+			</div>
+		';
+		list($p) = $this->process_directives( $html );
+		$this->assertNull( $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-context` directive doesn't overwrite context on
+	 * context without value.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_context_directive_doesnt_overwrite_context_on_context_without_value() {
+		$html    = '
+			<div data-wp-context=\'myPlugin::{ "id": "some-id-1" }\'>
+				<div data-wp-context>
+					<div class="test" data-wp-bind--id="myPlugin::context.id">Text</div>
+				</div>
+				<div class="test" data-wp-bind--id="myPlugin::context.id">Text</div>
+			</div>
+		';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-id-1', $p->get_attribute( 'id' ) );
+		$p->next_tag( array( 'class_name' => 'test' ) );
+		$this->assertEquals( 'some-id-1', $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-context` directive works with multiple directives.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_context_works_with_multiple_directives() {
+		$html    = '
+			<div data-wp-context=\'myPlugin::{ "id": "some-id" }\' data-wp-context=\'myPlugin::{ "id": "some-id" }\'>
+				<div class="test" data-wp-bind--id="myPlugin::context.id">Text</div>
+			</div>
+		';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-id', $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-context` directive doesn't work without any
+	 * namespace.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_context_directive_doesnt_work_without_any_namespace() {
+		$html    = '
+			<div data-wp-context=\'{ "id": "some-id" }\'>
+				<div class="test" data-wp-bind--id="context.id">Text</div>
+			</div>
+		';
+		list($p) = $this->process_directives( $html );
+		$this->assertNull( $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-context` directive works with a default namespace.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_context_directive_works_with_default_namespace() {
+		$html    = '
+			<div
+			 data-wp-interactive=\'{ "namespace": "myPlugin" }\'
+			 data-wp-context=\'{ "id": "some-id" }\'
+			>
+				<div class="test" data-wp-bind--id="context.id">Text</div>
+			</div>
+		';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-id', $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-context` directive overrides a default namespace.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_context_directive_overrides_default_namespace() {
+		$html    = '
+			<div
+			 data-wp-interactive=\'{ "namespace": "myPlugin" }\'
+			 data-wp-context=\'otherPlugin::{ "id": "some-id" }\'
+			>
+				<div data-wp-interactive=\'{ "namespace": "otherPlugin" }\'>
+					<div class="test" data-wp-bind--id="context.id">Text</div>
+				</div>
+			</div>
+		';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-id', $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-context` directive overrides the default namespace
+	 * with the same namespace.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_context_directive_overrides_default_namespace_with_same_namespace() {
+		$html    = '
+			<div
+			 data-wp-interactive=\'{ "namespace": "myPlugin" }\'
+			 data-wp-context=\'myPlugin::{ "id": "some-id" }\'
+			>
+				<div class="test" data-wp-bind--id="context.id">Text</div>
+			</div>
+		';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-id', $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-context` directive works with nested default
+	 * namespaces.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_context_directive_works_with_nested_default_namespaces() {
+		$html    = '
+			<div data-wp-interactive=\'{ "namespace": "myPlugin" }\'>
+				<div data-wp-context=\'{ "id": "some-id" }\'>
+					<div data-wp-interactive=\'{ "namespace": "otherPlugin" }\'>
+						<div data-wp-context=\'{ "id": "other-id" }\'>
+							<div class="test" data-wp-bind--id="context.id">Text</div>
+							<div class="test" data-wp-bind--id="myPlugin::context.id">Text</div>
+						</div>
+					</div>
+					<div class="test" data-wp-bind--id="context.id">Text</div>
+				</div>
+				<div class="test" data-wp-bind--id="context.id">Text</div>
+			</div>
+		';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'other-id', $p->get_attribute( 'id' ) );
+		$p->next_tag( array( 'class_name' => 'test' ) );
+		$this->assertEquals( 'some-id', $p->get_attribute( 'id' ) );
+		$p->next_tag( array( 'class_name' => 'test' ) );
+		$this->assertEquals( 'some-id', $p->get_attribute( 'id' ) );
+		$p->next_tag( array( 'class_name' => 'test' ) );
+		$this->assertNull( $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-context` directive works with a default namespace
+	 * in the same tag.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_context_directive_works_with_default_namespace_in_the_same_tag() {
+		$html    = '
+			<div
+			 class="test"
+			 data-wp-interactive=\'{ "namespace": "myPlugin" }\'
+			 data-wp-context=\'{ "id": "some-id" }\'
+			 data-wp-bind--id="context.id"
+			>
+				Text
+			</div>
+		';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-id', $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-context` directive merges the context in the same
+	 * default namespace.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_context_directive_merges_context_in_the_same_default_namespace() {
+		$html    = '
+			<div
+				data-wp-interactive=\'{ "namespace": "myPlugin" }\'
+				data-wp-context=\'{ "id1": "some-id-1" }\'
+			>
+				<div data-wp-context=\'{ "id2": "some-id-2" }\'>
+					<div class="test" data-wp-bind--id="context.id1">Text</div>
+					<div class="test" data-wp-bind--id="context.id2">Text</div>
+				</div>
+			</div>
+		';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-id-1', $p->get_attribute( 'id' ) );
+		$p->next_tag( array( 'class_name' => 'test' ) );
+		$this->assertEquals( 'some-id-2', $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-context` directive overwrites context in the same
+	 * default namespace.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_context_directive_overwrites_context_in_the_same_default_namespace() {
+		$html    = '
+			<div
+				data-wp-interactive=\'{ "namespace": "myPlugin" }\'
+				data-wp-context=\'{ "id": "some-id-1" }\'
+			>
+				<div data-wp-context=\'{ "id": "some-id-2" }\'>
+					<div class="test" data-wp-bind--id="context.id">Text</div>
+				</div>
+			</div>
+		';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-id-2', $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-context` directive replaces the old context after
+	 * the closing tag in the same default namespace.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_context_directive_replaces_old_context_after_closing_tag_in_the_same_default_namespace() {
+		$html    = '
+			<div
+				data-wp-interactive=\'{ "namespace": "myPlugin" }\'
+				data-wp-context=\'{ "id": "some-id-1" }\'
+			>
+				<div data-wp-context=\'{ "id": "some-id-2" }\'>
+					<div class="test" data-wp-bind--id="context.id">Text</div>
+				</div>
+				<div class="test" data-wp-bind--id="context.id">Text</div>
+			</div>
+		';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-id-2', $p->get_attribute( 'id' ) );
+		$p->next_tag( array( 'class_name' => 'test' ) );
+		$this->assertEquals( 'some-id-1', $p->get_attribute( 'id' ) );
+	}
+}
diff --git a/tests/phpunit/tests/interactivity-api/wpInteractivityAPI-wp-each.php b/tests/phpunit/tests/interactivity-api/wpInteractivityAPI-wp-each.php
new file mode 100644
index 0000000000000..eea7f3f9fe8e7
--- /dev/null
+++ b/tests/phpunit/tests/interactivity-api/wpInteractivityAPI-wp-each.php
@@ -0,0 +1,681 @@
+<?php
+/**
+ * Unit tests covering the data_wp_each_processor functionality of the
+ * WP_Interactivity_API class.
+ *
+ * @package WordPress
+ * @subpackage Interactivity API
+ *
+ * @group interactivity-api
+ */
+class Tests_WP_Interactivity_API_WP_Each extends WP_UnitTestCase {
+	/**
+	 * Instance of WP_Interactivity_API.
+	 *
+	 * @var WP_Interactivity_API
+	 */
+	protected $interactivity;
+
+	/**
+	 * Set up.
+	 */
+	public function set_up() {
+		parent::set_up();
+		$this->interactivity = new WP_Interactivity_API();
+		$this->interactivity->state( 'myPlugin', array( 'list' => array( 1, 2 ) ) );
+		$this->interactivity->state( 'myPlugin', array( 'after' => 'after-wp-each' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-each` directive doesn't do anything if it's not on
+	 * a template tag.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_each_doesnt_do_anything_on_non_template_tags() {
+		$original = '
+			<div data-wp-each="myPlugin::state.list">
+				<span data-wp-text="myPlugin::context.item"></span>
+			</div>';
+		$new      = $this->interactivity->process_directives( $original );
+		$this->assertEquals( $original, $new );
+	}
+
+	/**
+	 * Tests that the `data-wp-each` directive doesn't do anything if the array
+	 * is associative instead of indexed.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_each_doesnt_do_anything_on_associative_arrays() {
+		$this->interactivity->state(
+			'myPlugin',
+			array(
+				'assoc' => array(
+					'one' => 1,
+					'two' => 2,
+				),
+			)
+		);
+		$original = '
+			<template data-wp-each="myPlugin::state.assoc">
+				<span data-wp-text="myPlugin::context.item"></span>
+			</template>';
+		$new      = $this->interactivity->process_directives( $original );
+		$this->assertEquals( $original, $new );
+	}
+
+	/**
+	 * Tests that the `data-wp-each` directive works with simple tags.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_each_simple_tags() {
+		$original = '' .
+			'<template data-wp-each="myPlugin::state.list">' .
+				'<span data-wp-text="myPlugin::context.item"></span>' .
+			'</template>' .
+			'<div data-wp-bind--id="myPlugin::state.after">Text</div>';
+		$expected = '' .
+			'<template data-wp-each="myPlugin::state.list">' .
+				'<span data-wp-text="myPlugin::context.item"></span>' .
+			'</template>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.item">1</span>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.item">2</span>' .
+			'<div id="after-wp-each" data-wp-bind--id="myPlugin::state.after">Text</div>';
+		$new      = $this->interactivity->process_directives( $original );
+		$this->assertEquals( $expected, $new );
+	}
+
+	/**
+	 * Tests that the `data-wp-each` directive doesn't do anything if the array is
+	 * empty.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_each_empty_array() {
+		$this->interactivity->state( 'myPlugin', array( 'empty' => array() ) );
+		$original = '' .
+			'<template data-wp-each="myPlugin::state.empty">' .
+				'<span data-wp-text="myPlugin::context.item"></span>' .
+			'</template>' .
+			'<div data-wp-bind--id="myPlugin::state.after">Text</div>';
+		$expected = '' .
+			'<template data-wp-each="myPlugin::state.empty">' .
+				'<span data-wp-text="myPlugin::context.item"></span>' .
+			'</template>' .
+			'<div id="after-wp-each" data-wp-bind--id="myPlugin::state.after">Text</div>';
+		$new      = $this->interactivity->process_directives( $original );
+		$this->assertEquals( $expected, $new );
+	}
+
+	/**
+	 * Tests that the `data-wp-each` directive merges the item with the previous
+	 * context correctly.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_each_merges_context_correctly() {
+		$original = '' .
+			'<div data-wp-context=\'myPlugin::{ "item": "New text", "id": "some-id", "after": "after-wp-each" }\'>' .
+				'<template data-wp-each="myPlugin::state.list">' .
+					'<span data-wp-bind--id="myPlugin::context.id" data-wp-text="myPlugin::context.item"></span>' .
+				'</template>' .
+				'<div data-wp-bind--id="myPlugin::context.after" data-wp-text="myPlugin::context.item">Text</div>' .
+			'</div>';
+		$expected = '' .
+			'<div data-wp-context=\'myPlugin::{ "item": "New text", "id": "some-id", "after": "after-wp-each" }\'>' .
+				'<template data-wp-each="myPlugin::state.list">' .
+					'<span data-wp-bind--id="myPlugin::context.id" data-wp-text="myPlugin::context.item"></span>' .
+				'</template>' .
+				'<span data-wp-each-child id="some-id" data-wp-bind--id="myPlugin::context.id" data-wp-text="myPlugin::context.item">1</span>' .
+				'<span data-wp-each-child id="some-id" data-wp-bind--id="myPlugin::context.id" data-wp-text="myPlugin::context.item">2</span>' .
+				'<div id="after-wp-each" data-wp-bind--id="myPlugin::context.after" data-wp-text="myPlugin::context.item">New text</div>' .
+			'</div>';
+		$new      = $this->interactivity->process_directives( $original );
+		$this->assertEquals( $expected, $new );
+	}
+
+	/**
+	 * Tests that the `data-wp-each` directive works with arrays from the context.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_each_gets_arrays_from_context() {
+		$original = '' .
+			'<div data-wp-context=\'myPlugin::{ "list": [ 1, 2 ] }\'>' .
+				'<template data-wp-each="myPlugin::context.list">' .
+					'<span data-wp-text="myPlugin::context.item"></span>' .
+				'</template>' .
+				'<div data-wp-bind--id="myPlugin::state.after">Text</div>' .
+			'</div>';
+		$expected = '' .
+			'<div data-wp-context=\'myPlugin::{ "list": [ 1, 2 ] }\'>' .
+				'<template data-wp-each="myPlugin::context.list">' .
+					'<span data-wp-text="myPlugin::context.item"></span>' .
+				'</template>' .
+				'<span data-wp-each-child data-wp-text="myPlugin::context.item">1</span>' .
+				'<span data-wp-each-child data-wp-text="myPlugin::context.item">2</span>' .
+				'<div id="after-wp-each" data-wp-bind--id="myPlugin::state.after">Text</div>' .
+			'</div>';
+		$new      = $this->interactivity->process_directives( $original );
+		$this->assertEquals( $expected, $new );
+	}
+
+	/**
+	 * Tests that the `data-wp-each` directive works with the default namespace.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_each_default_namespace() {
+		$original = '' .
+			'<div data-wp-interactive=\'{ "namespace": "myPlugin" }\'>' .
+				'<template data-wp-each="state.list">' .
+					'<span data-wp-text="context.item"></span>' .
+				'</template>' .
+				'<div data-wp-bind--id="state.after">Text</div>' .
+			'</div>';
+		$expected = '' .
+			'<div data-wp-interactive=\'{ "namespace": "myPlugin" }\'>' .
+				'<template data-wp-each="state.list">' .
+					'<span data-wp-text="context.item"></span>' .
+				'</template>' .
+				'<span data-wp-each-child data-wp-text="context.item">1</span>' .
+				'<span data-wp-each-child data-wp-text="context.item">2</span>' .
+				'<div id="after-wp-each" data-wp-bind--id="state.after">Text</div>' .
+			'</div>';
+		$new      = $this->interactivity->process_directives( $original );
+		$this->assertEquals( $expected, $new );
+	}
+
+	/**
+	 * Tests that the `data-wp-each` directive works with multiple tags per item.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_each_multiple_tags_per_item() {
+		$original = '' .
+			'<template data-wp-each="myPlugin::state.list">' .
+				'<span data-wp-text="myPlugin::context.item"></span>' .
+				'<span data-wp-text="myPlugin::context.item"></span>' .
+			'</template>' .
+			'<div data-wp-bind--id="myPlugin::state.after">Text</div>';
+		$expected = '' .
+			'<template data-wp-each="myPlugin::state.list">' .
+				'<span data-wp-text="myPlugin::context.item"></span>' .
+				'<span data-wp-text="myPlugin::context.item"></span>' .
+			'</template>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.item">1</span>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.item">1</span>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.item">2</span>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.item">2</span>' .
+			'<div id="after-wp-each" data-wp-bind--id="myPlugin::state.after">Text</div>';
+		$new      = $this->interactivity->process_directives( $original );
+		$this->assertEquals( $expected, $new );
+	}
+
+	/**
+	 * Tests that the `data-wp-each` directive works with void tags.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_each_void_tags() {
+		$original = '' .
+			'<template data-wp-each="myPlugin::state.list">' .
+				'<img data-wp-bind--id="myPlugin::context.item">' .
+				'<img data-wp-bind--id="myPlugin::context.item">' .
+			'</template>' .
+			'<div data-wp-bind--id="myPlugin::state.after">Text</div>';
+		$expected = '' .
+			'<template data-wp-each="myPlugin::state.list">' .
+				'<img data-wp-bind--id="myPlugin::context.item">' .
+				'<img data-wp-bind--id="myPlugin::context.item">' .
+			'</template>' .
+			'<img data-wp-each-child id="1" data-wp-bind--id="myPlugin::context.item">' .
+			'<img data-wp-each-child id="1" data-wp-bind--id="myPlugin::context.item">' .
+			'<img data-wp-each-child id="2" data-wp-bind--id="myPlugin::context.item">' .
+			'<img data-wp-each-child id="2" data-wp-bind--id="myPlugin::context.item">' .
+			'<div id="after-wp-each" data-wp-bind--id="myPlugin::state.after">Text</div>';
+		$new      = $this->interactivity->process_directives( $original );
+		$this->assertEquals( $expected, $new );
+	}
+
+	/**
+	 * Tests that the `data-wp-each` directive works with combinations of void and
+	 * non-void tags.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_each_void_and_non_void_tags() {
+		$original = '' .
+			'<template data-wp-each="myPlugin::state.list">' .
+				'<img data-wp-bind--id="myPlugin::context.item">' .
+				'<span data-wp-text="myPlugin::context.item"></span>' .
+			'</template>' .
+			'<div data-wp-bind--id="myPlugin::state.after">Text</div>';
+		$expected = '' .
+			'<template data-wp-each="myPlugin::state.list">' .
+				'<img data-wp-bind--id="myPlugin::context.item">' .
+				'<span data-wp-text="myPlugin::context.item"></span>' .
+			'</template>' .
+			'<img data-wp-each-child id="1" data-wp-bind--id="myPlugin::context.item">' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.item">1</span>' .
+			'<img data-wp-each-child id="2" data-wp-bind--id="myPlugin::context.item">' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.item">2</span>' .
+			'<div id="after-wp-each" data-wp-bind--id="myPlugin::state.after">Text</div>';
+		$new      = $this->interactivity->process_directives( $original );
+		$this->assertEquals( $expected, $new );
+	}
+
+	/**
+	 * Tests that the `data-wp-each` directive works with nested tags.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_each_nested_tags() {
+		$original = '' .
+			'<template data-wp-each="myPlugin::state.list">' .
+				'<div data-wp-bind--id="myPlugin::context.item">' .
+					'id: <span data-wp-text="myPlugin::context.item"></span>' .
+				'</div>' .
+			'</template>' .
+			'<div data-wp-bind--id="myPlugin::state.after">Text</div>';
+		$expected = '' .
+			'<template data-wp-each="myPlugin::state.list">' .
+				'<div data-wp-bind--id="myPlugin::context.item">' .
+					'id: <span data-wp-text="myPlugin::context.item"></span>' .
+				'</div>' .
+			'</template>' .
+			'<div data-wp-each-child id="1" data-wp-bind--id="myPlugin::context.item">' .
+				'id: <span data-wp-text="myPlugin::context.item">1</span>' .
+			'</div>' .
+			'<div data-wp-each-child id="2" data-wp-bind--id="myPlugin::context.item">' .
+				'id: <span data-wp-text="myPlugin::context.item">2</span>' .
+			'</div>' .
+			'<div id="after-wp-each" data-wp-bind--id="myPlugin::state.after">Text</div>';
+		$new      = $this->interactivity->process_directives( $original );
+		$this->assertEquals( $expected, $new );
+	}
+
+	/**
+	 * Tests that the `data-wp-each` directive works with nested item properties.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_each_nested_item_properties() {
+		$this->interactivity->state(
+			'myPlugin',
+			array(
+				'list' => array(
+					array(
+						'id'   => 1,
+						'name' => 'one',
+					),
+					array(
+						'id'   => 2,
+						'name' => 'two',
+					),
+				),
+			)
+		);
+		$original = '' .
+			'<template data-wp-each="myPlugin::state.list">' .
+				'<span data-wp-text="myPlugin::context.item.id"></span>' .
+				'<span data-wp-text="myPlugin::context.item.name"></span>' .
+			'</template>' .
+			'<div data-wp-bind--id="myPlugin::state.after">Text</div>';
+		$expected = '' .
+			'<template data-wp-each="myPlugin::state.list">' .
+				'<span data-wp-text="myPlugin::context.item.id"></span>' .
+				'<span data-wp-text="myPlugin::context.item.name"></span>' .
+			'</template>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.item.id">1</span>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.item.name">one</span>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.item.id">2</span>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.item.name">two</span>' .
+			'<div id="after-wp-each" data-wp-bind--id="myPlugin::state.after">Text</div>';
+		$new      = $this->interactivity->process_directives( $original );
+		$this->assertEquals( $expected, $new );
+	}
+
+	/**
+	 * Tests that the `data-wp-each` directive works with different item names.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_each_different_item_names() {
+		$original = '' .
+			'<template data-wp-each--myitem="myPlugin::state.list">' .
+				'<span data-wp-text="myPlugin::context.myitem"></span>' .
+			'</template>' .
+			'<div data-wp-bind--id="myPlugin::state.after">Text</div>';
+		$expected = '' .
+			'<template data-wp-each--myitem="myPlugin::state.list">' .
+				'<span data-wp-text="myPlugin::context.myitem"></span>' .
+			'</template>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.myitem">1</span>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.myitem">2</span>' .
+			'<div id="after-wp-each" data-wp-bind--id="myPlugin::state.after">Text</div>';
+		$new      = $this->interactivity->process_directives( $original );
+		$this->assertEquals( $expected, $new );
+	}
+
+	/**
+	 * Tests that the `data-wp-each` directive transforms kebab-case into
+	 * camelCase.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_each_different_item_names_transforms_camelcase() {
+		$original = '' .
+			'<template data-wp-each--my-item="myPlugin::state.list">' .
+				'<span data-wp-text="myPlugin::context.myItem"></span>' .
+			'</template>' .
+			'<div data-wp-bind--id="myPlugin::state.after">Text</div>';
+		$expected = '' .
+			'<template data-wp-each--my-item="myPlugin::state.list">' .
+				'<span data-wp-text="myPlugin::context.myItem"></span>' .
+			'</template>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.myItem">1</span>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.myItem">2</span>' .
+			'<div id="after-wp-each" data-wp-bind--id="myPlugin::state.after">Text</div>';
+		$new      = $this->interactivity->process_directives( $original );
+		$this->assertEquals( $expected, $new );
+	}
+
+	/**
+	 * Tests that the `data-wp-each` directive doesn't work with top-level texts.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_each_doesnt_work_with_top_level_text() {
+		$original = '' .
+			'<template data-wp-each="myPlugin::state.list">' .
+				'id: <span data-wp-text="myPlugin::context.item"></span>' .
+			'</template>';
+		$new      = $this->interactivity->process_directives( $original );
+		$this->assertEquals( $original, $new );
+
+		$original = '' .
+			'<template data-wp-each="myPlugin::state.list">' .
+				'<span data-wp-text="myPlugin::context.item"></span>!' .
+			'</template>';
+		$new      = $this->interactivity->process_directives( $original );
+		$this->assertEquals( $original, $new );
+
+		// But it should work fine with spaces and linebreaks.
+		$original = '
+			<template data-wp-each="myPlugin::state.list">
+				<span class="test" data-wp-bind--id="myPlugin::context.item"></span>
+			</template>';
+		$new      = $this->interactivity->process_directives( $original );
+		$p        = new WP_HTML_Tag_Processor( $new );
+		$p->next_tag( array( 'class_name' => 'test' ) );
+		$p->next_tag( array( 'class_name' => 'test' ) );
+		$this->assertEquals( '1', $p->get_attribute( 'id' ) );
+		$p->next_tag( array( 'class_name' => 'test' ) );
+		$this->assertEquals( '2', $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-each` directive works with nested template tags.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_each_nested_template_tags() {
+		$this->interactivity->state( 'myPlugin', array( 'list2' => array( 3, 4 ) ) );
+		$original = '' .
+			'<template data-wp-each--item1="myPlugin::state.list">' .
+				'<span data-wp-text="myPlugin::context.item1"></span>' .
+				'<template data-wp-each--item2="myPlugin::state.list2">' .
+					'<span data-wp-text="myPlugin::context.item2"></span>' .
+				'</template>' .
+			'</template>' .
+			'<div data-wp-bind--id="myPlugin::state.after">Text</div>';
+		$expected = '' .
+			'<template data-wp-each--item1="myPlugin::state.list">' .
+				'<span data-wp-text="myPlugin::context.item1"></span>' .
+				'<template data-wp-each--item2="myPlugin::state.list2">' .
+					'<span data-wp-text="myPlugin::context.item2"></span>' .
+				'</template>' .
+			'</template>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.item1">1</span>' .
+			'<template data-wp-each-child data-wp-each--item2="myPlugin::state.list2">' .
+				'<span data-wp-text="myPlugin::context.item2"></span>' .
+			'</template>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.item2">3</span>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.item2">4</span>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.item1">2</span>' .
+			'<template data-wp-each-child data-wp-each--item2="myPlugin::state.list2">' .
+				'<span data-wp-text="myPlugin::context.item2"></span>' .
+			'</template>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.item2">3</span>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.item2">4</span>' .
+			'<div id="after-wp-each" data-wp-bind--id="myPlugin::state.after">Text</div>';
+		$new      = $this->interactivity->process_directives( $original );
+		$this->assertEquals( $expected, $new );
+	}
+
+	/**
+	 * Tests that the `data-wp-each` directive works with directly nested template
+	 * tags.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_each_directly_nested_template_tags() {
+		$this->interactivity->state( 'myPlugin', array( 'list2' => array( 3, 4 ) ) );
+		$original = '' .
+			'<template data-wp-each--item1="myPlugin::state.list">' .
+				'<template data-wp-each--item2="myPlugin::state.list2">' .
+					'<span data-wp-text="myPlugin::context.item1"></span>' .
+					'<span data-wp-text="myPlugin::context.item2"></span>' .
+				'</template>' .
+			'</template>' .
+			'<div data-wp-bind--id="myPlugin::state.after">Text</div>';
+		$expected = '' .
+			'<template data-wp-each--item1="myPlugin::state.list">' .
+				'<template data-wp-each--item2="myPlugin::state.list2">' .
+					'<span data-wp-text="myPlugin::context.item1"></span>' .
+					'<span data-wp-text="myPlugin::context.item2"></span>' .
+				'</template>' .
+			'</template>' .
+			'<template data-wp-each-child data-wp-each--item2="myPlugin::state.list2">' .
+				'<span data-wp-text="myPlugin::context.item1"></span>' .
+				'<span data-wp-text="myPlugin::context.item2"></span>' .
+			'</template>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.item1">1</span>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.item2">3</span>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.item1">1</span>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.item2">4</span>' .
+			'<template data-wp-each-child data-wp-each--item2="myPlugin::state.list2">' .
+				'<span data-wp-text="myPlugin::context.item1"></span>' .
+				'<span data-wp-text="myPlugin::context.item2"></span>' .
+			'</template>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.item1">2</span>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.item2">3</span>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.item1">2</span>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.item2">4</span>' .
+			'<div id="after-wp-each" data-wp-bind--id="myPlugin::state.after">Text</div>';
+		$new      = $this->interactivity->process_directives( $original );
+		$this->assertEquals( $expected, $new );
+	}
+
+	/**
+	 * Tests that the `data-wp-each` directive works with nestded template tags
+	 * that use a previous item as a list.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_each_nested_template_tags_using_previous_item_as_list() {
+		$this->interactivity->state( 'myPlugin', array( 'list2' => array( array( 1, 2 ), array( 3, 4 ) ) ) );
+		$original = '' .
+			'<template data-wp-each--list="myPlugin::state.list2">' .
+				'<template data-wp-each--number="myPlugin::context.list">' .
+					'<span data-wp-text="myPlugin::context.number"></span>' .
+				'</template>' .
+			'</template>' .
+			'<div data-wp-bind--id="myPlugin::state.after">Text</div>';
+		$expected = '' .
+			'<template data-wp-each--list="myPlugin::state.list2">' .
+				'<template data-wp-each--number="myPlugin::context.list">' .
+					'<span data-wp-text="myPlugin::context.number"></span>' .
+				'</template>' .
+			'</template>' .
+			'<template data-wp-each-child data-wp-each--number="myPlugin::context.list">' .
+				'<span data-wp-text="myPlugin::context.number"></span>' .
+			'</template>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.number">1</span>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.number">2</span>' .
+			'<template data-wp-each-child data-wp-each--number="myPlugin::context.list">' .
+				'<span data-wp-text="myPlugin::context.number"></span>' .
+			'</template>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.number">3</span>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.number">4</span>' .
+			'<div id="after-wp-each" data-wp-bind--id="myPlugin::state.after">Text</div>';
+		$new      = $this->interactivity->process_directives( $original );
+		$this->assertEquals( $expected, $new );
+	}
+
+	/**
+	 * Tests that the `data-wp-each` directive doesn't process unbalanced tags.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_each_unbalanced_tags() {
+		$original = '' .
+			'<template data-wp-each="myPlugin::state.list">' .
+				'<span data-wp-text="myPlugin::context.item">' .
+			'</template>' .
+			'<div data-wp-bind--id="myPlugin::state.after">Text</div>';
+		$new      = $this->interactivity->process_directives( $original );
+		$this->assertEquals( $original, $new );
+	}
+
+	/**
+	 * Tests that the `data-wp-each` directive doesn't process unbalanced tags in
+	 * nested templates.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_each_unbalanced_tags_in_nested_template_tags() {
+		$this->interactivity->state( 'myPlugin', array( 'list2' => array( 3, 4 ) ) );
+		$original = '' .
+			'<template data-wp-each--item1="myPlugin::state.list">' .
+				'<span data-wp-text="myPlugin::context.item1"></span>' .
+				'<template data-wp-each--item2="myPlugin::state.list2">' .
+					'<span data-wp-text="myPlugin::context.item2">' .
+				'</template>' .
+			'</template>' .
+			'<div data-wp-bind--id="myPlugin::state.after">Text</div>';
+		$new      = $this->interactivity->process_directives( $original );
+		$this->assertEquals( $original, $new );
+	}
+
+	/**
+	 * Tests that the `data-wp-each` directive doesn't process if it doesn't get
+	 * an array.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_each_doesnt_process_if_not_array() {
+		$original = '' .
+			'<template data-wp-each="myPlugin::state.list">' .
+				'<span data-wp-text="myPlugin::context.item"></span>' .
+			'</template>' .
+			'<div data-wp-bind--id="myPlugin::state.after">Text</div>';
+		$expected = '' .
+			'<template data-wp-each="myPlugin::state.list">' .
+				'<span data-wp-text="myPlugin::context.item"></span>' .
+			'</template>' .
+			'<div id="after-wp-each" data-wp-bind--id="myPlugin::state.after">Text</div>';
+
+		$this->interactivity->state( 'myPlugin', array( 'list' => null ) );
+		$new = $this->interactivity->process_directives( $original );
+		$this->assertEquals( $expected, $new );
+
+		$this->interactivity->state( 'myPlugin', array( 'list' => 'Text' ) );
+		$new = $this->interactivity->process_directives( $original );
+		$this->assertEquals( $expected, $new );
+
+		$this->interactivity->state( 'myPlugin', array( 'list' => 100 ) );
+		$new = $this->interactivity->process_directives( $original );
+		$this->assertEquals( $expected, $new );
+
+		$this->interactivity->state( 'myPlugin', array( 'list' => false ) );
+		$new = $this->interactivity->process_directives( $original );
+		$this->assertEquals( $expected, $new );
+
+		$this->interactivity->state( 'myPlugin', array( 'list' => true ) );
+		$new = $this->interactivity->process_directives( $original );
+		$this->assertEquals( $expected, $new );
+	}
+
+	/**
+	 * Tests that the `data-wp-each` directive doesn't process anything if it
+	 * detects manual server-side processing.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_each_doesnt_process_with_manual_server_directive_processing() {
+		$original = '' .
+			'<template data-wp-each="myPlugin::state.list">' .
+				'<span data-wp-text="myPlugin::context.item"></span>' .
+			'</template>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.item">1</span>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.item">2</span>' .
+			'<div data-wp-bind--id="myPlugin::state.after">Text</div>';
+		$expected = '' .
+			'<template data-wp-each="myPlugin::state.list">' .
+				'<span data-wp-text="myPlugin::context.item"></span>' .
+			'</template>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.item">1</span>' .
+			'<span data-wp-each-child data-wp-text="myPlugin::context.item">2</span>' .
+			'<div id="after-wp-each" data-wp-bind--id="myPlugin::state.after">Text</div>';
+		$new      = $this->interactivity->process_directives( $original );
+		$this->assertEquals( $expected, $new );
+	}
+}
diff --git a/tests/phpunit/tests/interactivity-api/wpInteractivityAPI-wp-interactive.php b/tests/phpunit/tests/interactivity-api/wpInteractivityAPI-wp-interactive.php
new file mode 100644
index 0000000000000..277287a553ba3
--- /dev/null
+++ b/tests/phpunit/tests/interactivity-api/wpInteractivityAPI-wp-interactive.php
@@ -0,0 +1,266 @@
+<?php
+/**
+ * Unit tests covering the data_wp_interactive_processor functionality of the
+ * WP_Interactivity_API class.
+ *
+ * @package WordPress
+ * @subpackage Interactivity API
+ *
+ * @since 6.5.0
+ *
+ * @group interactivity-api
+ */
+class Tests_WP_Interactivity_API_WP_Interactive extends WP_UnitTestCase {
+	/**
+	 * Instance of WP_Interactivity_API.
+	 *
+	 * @var WP_Interactivity_API
+	 */
+	protected $interactivity;
+
+	/**
+	 * Set up.
+	 */
+	public function set_up() {
+		parent::set_up();
+		$this->interactivity = new WP_Interactivity_API();
+		$this->interactivity->state( 'myPlugin', array( 'id' => 'some-id' ) );
+		$this->interactivity->state( 'otherPlugin', array( 'id' => 'other-id' ) );
+	}
+
+	/**
+	 * Invokes the `process_directives` method of WP_Interactivity_API class.
+	 *
+	 * @param string $html The HTML that needs to be processed.
+	 * @return array An array containing an instance of the WP_HTML_Tag_Processor and the processed HTML.
+	 */
+	private function process_directives( $html ) {
+		$new_html = $this->interactivity->process_directives( $html );
+		$p        = new WP_HTML_Tag_Processor( $new_html );
+		$p->next_tag( array( 'class_name' => 'test' ) );
+		return array( $p, $new_html );
+	}
+
+	/**
+	 * Tests that a default namespace is applied when using the
+	 * `data-wp-interactive` directive with a json object.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_interactive_sets_a_default_namespace_with_object() {
+		$html    = '
+					<div data-wp-interactive=\'{ "namespace": "myPlugin" }\'>
+							<div class="test" data-wp-bind--id="state.id">Text</div>
+					</div>
+			';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-id', $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that a default namespace is applied when using the
+	 * `data-wp-interactive` directive with a string.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_interactive_sets_a_default_namespace_with_string() {
+		$html    = '
+					<div data-wp-interactive="myPlugin">
+							<div class="test" data-wp-bind--id="state.id">Text</div>
+					</div>
+			';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-id', $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that the most recent `data-wp-interactive` directive replaces the
+	 * previous default namespace.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_interactive_replaces_the_previous_default_namespace() {
+		$html    = '
+					<div data-wp-interactive=\'{ "namespace": "otherPlugin" }\'>
+							<div data-wp-interactive=\'{ "namespace": "myPlugin" }\'>
+									<div class="test" data-wp-bind--id="state.id">Text</div>
+							</div>
+							<div class="test" data-wp-bind--id="state.id">Text</div>
+					</div>
+			';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-id', $p->get_attribute( 'id' ) );
+		$p->next_tag( array( 'class_name' => 'test' ) );
+		$this->assertEquals( 'other-id', $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that a `data-wp-interactive` directive with a json object that
+	 * doesn't have a namespace property does not replace the previously
+	 * established default namespace.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_interactive_json_without_namespace_doesnt_replace_the_previous_default_namespace() {
+		$html    = '
+					<div data-wp-interactive=\'{ "namespace": "myPlugin" }\'>
+							<div data-wp-interactive=\'{}\'>
+									<div class="test" data-wp-bind--id="state.id">Text</div>
+							</div>
+							<div class="test" data-wp-bind--id="state.id">Text</div>
+					</div>
+			';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-id', $p->get_attribute( 'id' ) );
+		$p->next_tag( array( 'class_name' => 'test' ) );
+		$this->assertEquals( 'some-id', $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that an empty value for `data-wp-interactive` does not replace the
+	 * previously established default namespace.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_interactive_with_empty_value_doesnt_replace_the_previous_default_namespace() {
+		$html    = '
+					<div data-wp-interactive=\'{ "namespace": "myPlugin" }\'>
+							<div data-wp-interactive="">
+									<div class="test" data-wp-bind--id="state.id">Text</div>
+							</div>
+							<div class="test" data-wp-bind--id="state.id">Text</div>
+					</div>
+			';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-id', $p->get_attribute( 'id' ) );
+		$p->next_tag( array( 'class_name' => 'test' ) );
+		$this->assertEquals( 'some-id', $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that an invalid value for `data-wp-interactive` does not replace the
+	 * previously established default namespace.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_interactive_with_invalid_value_doesnt_replace_the_previous_default_namespace() {
+		$html    = '
+				<div data-wp-interactive=\'{ "namespace": "myPlugin" }\'>
+						<div data-wp-interactive="$myPlugin">
+								<div class="test" data-wp-bind--id="state.id">Text</div>
+						</div>
+						<div class="test" data-wp-bind--id="state.id">Text</div>
+				</div>
+		';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-id', $p->get_attribute( 'id' ) );
+		$p->next_tag( array( 'class_name' => 'test' ) );
+		$this->assertEquals( 'some-id', $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that a `data-wp-interactive` directive with no assigned value does
+	 * not replace the previously established default namespace.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_interactive_without_value_doesnt_replace_the_previous_default_namespace() {
+		$html    = '
+					<div data-wp-interactive=\'{ "namespace": "myPlugin" }\'>
+							<div data-wp-interactive>
+									<div class="test" data-wp-bind--id="state.id">Text</div>
+							</div>
+							<div class="test" data-wp-bind--id="state.id">Text</div>
+					</div>
+			';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-id', $p->get_attribute( 'id' ) );
+		$p->next_tag( array( 'class_name' => 'test' ) );
+		$this->assertEquals( 'some-id', $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that multiple `data-wp-interactive` directives work correctly.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_interactive_works_with_multiple_directives() {
+		$html    = '
+					<div data-wp-interactive=\'{ "namespace": "myPlugin" }\' data-wp-interactive=\'{ "namespace": "myPlugin" }\'>
+							<div class="test" data-wp-bind--id="state.id">Text</div>
+					</div>
+			';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-id', $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that a custom namespace can override the default one provided by a
+	 * `data-wp-interactive` directive.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_interactive_namespace_can_be_override_by_custom_one() {
+		$html    = '
+					<div data-wp-interactive=\'{ "namespace": "myPlugin" }\'>
+							<div class="test" data-wp-bind--id="otherPlugin::state.id">Text</div>
+					</div>
+			';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'other-id', $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-interactive` setting is reset appropriately after a
+	 * closing HTML tag.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_interactive_set_is_unset_on_closing_tag() {
+		$html    = '
+					<div data-wp-interactive=\'{ "namespace": "myPlugin" }\'>
+							<div class="test" data-wp-bind--id="state.id">Text</div>
+					</div>
+					<div data-wp-interactive=\'{ "namespace": "otherPlugin" }\'>
+							<div class="test" data-wp-bind--id="state.id">Text</div>
+					</div>
+			';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'some-id', $p->get_attribute( 'id' ) );
+		$p->next_tag( array( 'class_name' => 'test' ) );
+		$this->assertEquals( 'other-id', $p->get_attribute( 'id' ) );
+
+		$html    = '
+					<div data-wp-interactive=\'{ "namespace": "myPlugin" }\'>
+							<div data-wp-interactive=\'{ "namespace": "otherPlugin" }\'>
+									<div class="test" data-wp-bind--id="state.id">Text</div>
+							</div>
+							<div class="test" data-wp-bind--id="state.id">Text</div>
+					</div>
+			';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'other-id', $p->get_attribute( 'id' ) );
+		$p->next_tag( array( 'class_name' => 'test' ) );
+		$this->assertEquals( 'some-id', $p->get_attribute( 'id' ) );
+	}
+}
diff --git a/tests/phpunit/tests/interactivity-api/wpInteractivityAPI-wp-router-region.php b/tests/phpunit/tests/interactivity-api/wpInteractivityAPI-wp-router-region.php
new file mode 100644
index 0000000000000..a02ad6920b5a4
--- /dev/null
+++ b/tests/phpunit/tests/interactivity-api/wpInteractivityAPI-wp-router-region.php
@@ -0,0 +1,131 @@
+<?php
+/**
+ * Unit tests covering the `data_wp_router_region` processor functionality of
+ * the WP_Interactivity_API class.
+ *
+ * @package WordPress
+ * @subpackage Interactivity API
+ *
+ * @group interactivity-api
+ */
+class Tests_WP_Interactivity_API_WP_Router_Region extends WP_UnitTestCase {
+	/**
+	 * Instance of WP_Interactivity_API.
+	 *
+	 * @var WP_Interactivity_API
+	 */
+	protected $interactivity;
+
+	/**
+	 * Original WP_Hook instance associated to `wp_footer`.
+	 *
+	 * @var WP_Hook
+	 */
+	protected $original_wp_footer;
+
+	/**
+	 * Original instance associated to `wp_footer`.
+	 *
+	 * @var WP_Styles
+	 */
+	protected $original_wp_styles;
+
+	/**
+	 * Set up.
+	 */
+	public function set_up() {
+		parent::set_up();
+		$this->interactivity = new WP_Interactivity_API();
+
+		// Removes all hooks set for `wp_footer`.
+		global $wp_filter;
+		$this->original_wp_footer = $wp_filter['wp_footer'];
+		$wp_filter['wp_footer']   = new WP_Hook();
+
+		// Removes all registered styles.
+		$this->original_wp_styles = isset( $GLOBALS['wp_styles'] ) ? $GLOBALS['wp_styles'] : null;
+		$GLOBALS['wp_styles']     = new WP_Styles();
+		remove_action( 'wp_default_styles', 'wp_default_styles' );
+		remove_action( 'wp_print_styles', 'print_emoji_styles' );
+	}
+
+	/**
+	 * Tear down.
+	 */
+	public function tear_down() {
+		// Restores all previous hooks set for `wp_footer`.
+		global $wp_filter;
+		$wp_filter['wp_footer'] = $this->original_wp_footer;
+
+		// Restores all previous registered styles.
+		$GLOBALS['wp_styles'] = $this->original_wp_styles;
+		add_action( 'wp_default_styles', 'wp_default_styles' );
+		add_action( 'wp_print_styles', 'print_emoji_styles' );
+
+		parent::tear_down();
+	}
+
+	/**
+	 * Executes the hooks associated to `wp_footer`.
+	 */
+	protected function render_wp_footer() {
+		ob_start();
+		do_action( 'wp_footer' );
+		return ob_get_clean();
+	}
+
+	/**
+	 * Tests that no elements are added if the `data-wp-router-region` is
+	 * missing.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_router_region_missing() {
+		$html     = '<div>Nothing here</div>';
+		$new_html = $this->interactivity->process_directives( $html );
+		$footer   = $this->render_wp_footer();
+		$this->assertEquals( $html, $new_html );
+		$this->assertEquals( '', $footer );
+		$this->assertEquals( '', get_echo( 'wp_print_styles' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-router-region` directive adds a loading bar and a
+	 * region for screen reader announcements in the footer, and styles for the
+	 * loading bar. Also checks that the markup and styles are only added once.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_router_region_adds_loading_bar_aria_live_region_only_once() {
+		$html     = '
+			<div data-wp-router-region="region A">Interactive region</div>
+			<div data-wp-router-region="region B">Another interactive region</div>
+		';
+		$new_html = $this->interactivity->process_directives( $html );
+		$this->assertEquals( $html, $new_html );
+
+		// Check that the style is loaded, but only once.
+		$styles = get_echo( 'wp_print_styles' );
+		$query  = array( 'tag_name' => 'style' );
+		$p      = new WP_HTML_Tag_Processor( $styles );
+		$this->assertTrue( $p->next_tag( $query ) );
+		$this->assertEquals( 'wp-interactivity-router-animations-inline-css', $p->get_attribute( 'id' ) );
+		$this->assertStringContainsString( '.wp-interactivity-router-loading-bar', $styles );
+		$this->assertFalse( $p->next_tag( $query ) );
+
+		// Check that the markup is loaded, but only once.
+		$footer = $this->render_wp_footer();
+		$query  = array( 'class_name' => 'wp-interactivity-router-loading-bar' );
+		$p      = new WP_HTML_Tag_Processor( $footer );
+		$this->assertTrue( $p->next_tag( $query ) );
+		$this->assertFalse( $p->next_tag( $query ) );
+		$query = array( 'class_name' => 'screen-reader-text' );
+		$p     = new WP_HTML_Tag_Processor( $footer );
+		$this->assertTrue( $p->next_tag( $query ) );
+		$this->assertFalse( $p->next_tag( $query ) );
+	}
+}
diff --git a/tests/phpunit/tests/interactivity-api/wpInteractivityAPI-wp-style.php b/tests/phpunit/tests/interactivity-api/wpInteractivityAPI-wp-style.php
new file mode 100644
index 0000000000000..46fa541fb79cc
--- /dev/null
+++ b/tests/phpunit/tests/interactivity-api/wpInteractivityAPI-wp-style.php
@@ -0,0 +1,445 @@
+<?php
+/**
+ * Unit tests covering the data_wp_style_processor functionality of the
+ * WP_Interactivity_API class.
+ *
+ * @package WordPress
+ * @subpackage Interactivity API
+ *
+ * @since 6.5.0
+ *
+ * @group interactivity-api
+ */
+class Tests_WP_Interactivity_API_WP_Style extends WP_UnitTestCase {
+	/**
+	 * Instance of WP_Interactivity_API.
+	 *
+	 * @var WP_Interactivity_API
+	 */
+	protected $interactivity;
+
+	/**
+	 * Set up.
+	 */
+	public function set_up() {
+		parent::set_up();
+		$this->interactivity = new WP_Interactivity_API();
+		$this->interactivity->state(
+			'myPlugin',
+			array(
+				'green' => 'green',
+				'false' => false,
+			)
+		);
+	}
+
+	/**
+	 * Invokes the private `merge_style_property` method of WP_Interactivity_API
+	 * class.
+	 *
+	 * @param string            $style_attribute_value The current style attribute value.
+	 * @param string            $style_property_name   The style property name to set.
+	 * @param string|false|null $style_property_value  The value to set for the style property. With false, null or an
+	 *                                                 empty string, it removes the style property.
+	 * @return string The new style attribute value after the specified property has been added, updated or removed.
+	 */
+	private function merge_style_property( $style_attribute_value, $style_property_name, $style_property_value ) {
+		$evaluate = new ReflectionMethod( $this->interactivity, 'merge_style_property' );
+		$evaluate->setAccessible( true );
+		return $evaluate->invokeArgs( $this->interactivity, array( $style_attribute_value, $style_property_name, $style_property_value ) );
+	}
+
+	/**
+	 * Tests that `merge_style_property` correctly sets style properties.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::merge_style_property
+	 */
+	public function test_merge_style_property_sets_properties() {
+		// Adds property on empty style attribute.
+		$result = $this->merge_style_property( '', 'color', 'green' );
+		$this->assertEquals( 'color:green;', $result );
+
+		// Changes style property when there is an existing property.
+		$result = $this->merge_style_property( 'color:red;', 'color', 'green' );
+		$this->assertEquals( 'color:green;', $result );
+
+		// Adds a new property when the existing one does not match.
+		$result = $this->merge_style_property( 'color:red;', 'background', 'blue' );
+		$this->assertEquals( 'color:red;background:blue;', $result );
+
+		// Handles multiple existing properties.
+		$result = $this->merge_style_property( 'color:red;margin:5px;', 'color', 'green' );
+		$this->assertEquals( 'margin:5px;color:green;', $result );
+
+		// Adds a new property when multiple existing properties do not match.
+		$result = $this->merge_style_property( 'color:red;margin:5px;', 'padding', '10px' );
+		$this->assertEquals( 'color:red;margin:5px;padding:10px;', $result );
+
+		// Removes whitespaces in all properties.
+		$result = $this->merge_style_property( ' color : red; margin : 5px; ', 'padding', ' 10px ' );
+		$this->assertEquals( 'color:red;margin:5px;padding:10px;', $result );
+
+		// Updates a property when it's not the first one in the value.
+		$result = $this->merge_style_property( 'color:red;margin:5px;', 'margin', '15px' );
+		$this->assertEquals( 'color:red;margin:15px;', $result );
+
+		// Adds missing trailing semicolon.
+		$result = $this->merge_style_property( 'color:red;margin:5px', 'padding', '10px' );
+		$this->assertEquals( 'color:red;margin:5px;padding:10px;', $result );
+
+		// Doesn't add double semicolons.
+		$result = $this->merge_style_property( 'color:red;margin:5px;', 'padding', '10px;' );
+		$this->assertEquals( 'color:red;margin:5px;padding:10px;', $result );
+
+		// Handles empty properties in the input.
+		$result = $this->merge_style_property( 'color:red;;margin:5px;;', 'padding', '10px' );
+		$this->assertEquals( 'color:red;margin:5px;padding:10px;', $result );
+
+		// Moves the modified property to the end.
+		$result = $this->merge_style_property( 'border-style: dashed; border: 3px solid red;', 'border-style', 'inset' );
+		$this->assertEquals( 'border:3px solid red;border-style:inset;', $result );
+	}
+
+	/**
+	 * Tests that `merge_style_property` works correctly with falsy values,
+	 * removing or ignoring them as appropriate.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::merge_style_property
+	 */
+	public function test_merge_style_property_with_falsy_values() {
+		// Removes a property with an empty string.
+		$result = $this->merge_style_property( 'color:red;margin:5px;', 'color', '' );
+		$this->assertEquals( 'margin:5px;', $result );
+
+		// Removes a property with null.
+		$result = $this->merge_style_property( 'color:red;margin:5px;', 'color', null );
+		$this->assertEquals( 'margin:5px;', $result );
+
+		// Removes a property with false.
+		$result = $this->merge_style_property( 'color:red;margin:5px;', 'color', false );
+		$this->assertEquals( 'margin:5px;', $result );
+
+		// Removes a property with 0.
+		$result = $this->merge_style_property( 'color:red;margin:5px;', 'color', 0 );
+		$this->assertEquals( 'margin:5px;', $result );
+
+		// It doesn't add a new property with an empty string.
+		$result = $this->merge_style_property( 'color:red;', 'padding', '' );
+		$this->assertEquals( 'color:red;', $result );
+
+		// It doesn't add a new property with null.
+		$result = $this->merge_style_property( 'color:red;', 'padding', null );
+		$this->assertEquals( 'color:red;', $result );
+
+		// It doesn't add a new property with false.
+		$result = $this->merge_style_property( 'color:red;', 'padding', false );
+		$this->assertEquals( 'color:red;', $result );
+
+		// It doesn't add a new property with 0.
+		$result = $this->merge_style_property( 'color:red;', 'padding', 0 );
+		$this->assertEquals( 'color:red;', $result );
+	}
+
+	/**
+	 * Invokes the `process_directives` method of WP_Interactivity_API class.
+	 *
+	 * @param string $html The HTML that needs to be processed.
+	 * @return array An array containing an instance of the WP_HTML_Tag_Processor and the processed HTML.
+	 */
+	private function process_directives( $html ) {
+		$new_html = $this->interactivity->process_directives( $html );
+		$p        = new WP_HTML_Tag_Processor( $new_html );
+		$p->next_tag();
+		return array( $p, $new_html );
+	}
+
+	/**
+	 * Tests that the `data-wp-style` directive sets a style attribute with
+	 * correct property and value.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_style_sets_style_attribute() {
+		$html    = '<div data-wp-style--color="myPlugin::state.green">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'color:green;', $p->get_attribute( 'style' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-style` directive applies multiple style properties
+	 * correctly.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_style_sets_multiple_style_properties() {
+		$html    = '
+			<div
+				data-wp-style--color="myPlugin::state.green"
+				data-wp-style--background="myPlugin::state.green"
+			>Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'color:green;background:green;', $p->get_attribute( 'style' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-style` directive correctly handles different style
+	 * property values.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_style_sets_multiple_style_properties_with_different_values() {
+		$html    = '
+			<div
+				data-wp-style--color="myPlugin::state.green"
+				data-wp-style--background="myPlugin::state.false"
+			>Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'color:green;', $p->get_attribute( 'style' ) );
+
+		$html    = '
+			<div
+				style="background:red;"
+				data-wp-style--color="myPlugin::state.green"
+				data-wp-style--background="myPlugin::state.false"
+			>Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'color:green;', $p->get_attribute( 'style' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-style` directive sets a new style property when
+	 * another already exists.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_style_sets_style_property_when_style_attribute_exists() {
+		$html    = '<div style="padding:10px;" data-wp-style--color="myPlugin::state.green">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'padding:10px;color:green;', $p->get_attribute( 'style' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-style` directive overwrites an existing style
+	 * property with a new value.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_style_overwrites_style_property_when_style_property_exists() {
+		$html    = '<div style="color:red;" data-wp-style--color="myPlugin::state.green">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'color:green;', $p->get_attribute( 'style' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-style` directive doesn't add a style property when
+	 * the directive value is false.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_style_doesnt_add_style_attribute_on_false() {
+		$html    = '<div data-wp-style--color="myPlugin::state.false">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertNull( $p->get_attribute( 'style' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-style` directive doesn't modify existing style
+	 * properties when directive value is false.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_style_doesnt_add_style_property_on_false() {
+		$html    = '<div style="padding:10px;" data-wp-style--color="myPlugin::state.false">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'padding:10px;', $p->get_attribute( 'style' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-style` directive keeps an existing style property
+	 * with a matching value.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_style_keeps_style_property_when_style_property_exists() {
+		$html    = '<div style="color:green;" data-wp-style--color="myPlugin::state.green">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'color:green;', $p->get_attribute( 'style' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-style` directive maintains style properties even
+	 * when they aren't the only ones present.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_style_keeps_style_property_when_style_property_exists_and_is_not_the_only_one() {
+		$html    = '<div style="padding:10px;color:green;" data-wp-style--color="myPlugin::state.green">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'padding:10px;color:green;', $p->get_attribute( 'style' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-style` directive removes the style attribute when
+	 * it contains only one property which is being removed.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_style_removes_style_attribute_when_style_property_exists_and_is_the_only_one() {
+		$html    = '<div style="color:green;" data-wp-style--color="myPlugin::state.false">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertNull( $p->get_attribute( 'style' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-style` directive removes a style property when it's
+	 * not the only one present and the directive value is false.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_style_removes_style_property_when_style_property_exists_and_is_not_the_only_one() {
+		$html    = '<div style="padding:10px;color:green;" data-wp-style--color="myPlugin::state.false">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'padding:10px;', $p->get_attribute( 'style' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-style` directive does not remove an empty style
+	 * attribute.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_style_doesnt_remove_empty_style_attribute() {
+		$html    = '<div style data-wp-style--color="myPlugin::state.false">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertTrue( $p->get_attribute( 'style' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-style` directive does not change the style
+	 * attribute when the directive suffix is empty.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_style_doesnt_change_style_attribute_with_empty_directive_suffix() {
+		$html    = '<div style="padding:10px;" data-wp-style="myPlugin::state.green">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'padding:10px;', $p->get_attribute( 'style' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-style` directive does not change the style
+	 * attribute when the value of the directive is empty.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_style_doesnt_change_style_attribute_with_empty_value() {
+		$html    = '<div style="padding:10px" data-wp-style--color="">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'padding:10px;', $p->get_attribute( 'style' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-style` directive doesn't apply changes if no value
+	 * is provided for the style property.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_style_doesnt_change_style_attribute_without_value() {
+		$html    = '<div style="padding: 10px;" data-wp-style--color>Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'padding:10px;', $p->get_attribute( 'style' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-style` directive functions correctly with multiple
+	 * identical directives.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_style_works_with_multiple_directives() {
+		$html    = '<div data-wp-style--color="myPlugin::state.green" data-wp-style--color="myPlugin::state.green">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertEquals( 'color:green;', $p->get_attribute( 'style' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-style` directive doesn't apply any changes when the
+	 * state value is true.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_style_doesnt_do_anything_on_true_values() {
+		$this->interactivity->state( 'myPlugin', array( 'true' => true ) );
+		$html    = '<div data-wp-style--color="myPlugin::state.text">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertNull( $p->get_attribute( 'style' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-style` directive doesn't add a style property for
+	 * various falsy values in the state.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_style_doesnt_add_style_property_on_falsy_values() {
+		$this->interactivity->state( 'myPlugin', array( 'text' => '' ) );
+		$html    = '<div data-wp-style--color="myPlugin::state.text">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertNull( $p->get_attribute( 'style' ) );
+
+		$this->interactivity->state( 'myPlugin', array( 'array' => array() ) );
+		$html    = '<div data-wp-style--color="myPlugin::state.array">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertNull( $p->get_attribute( 'style' ) );
+
+		$this->interactivity->state( 'myPlugin', array( 'number' => 0 ) );
+		$html    = '<div data-wp-style--color="myPlugin::state.number">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertNull( $p->get_attribute( 'style' ) );
+
+		$this->interactivity->state( 'myPlugin', array( 'null' => null ) );
+		$html    = '<div data-wp-style--color="myPlugin::state.null">Text</div>';
+		list($p) = $this->process_directives( $html );
+		$this->assertNull( $p->get_attribute( 'style' ) );
+	}
+}
diff --git a/tests/phpunit/tests/interactivity-api/wpInteractivityAPI-wp-text.php b/tests/phpunit/tests/interactivity-api/wpInteractivityAPI-wp-text.php
new file mode 100644
index 0000000000000..b33ad7c82761f
--- /dev/null
+++ b/tests/phpunit/tests/interactivity-api/wpInteractivityAPI-wp-text.php
@@ -0,0 +1,153 @@
+<?php
+/**
+ * Unit tests covering the data_wp_text_processor functionality of the
+ * WP_Interactivity_API class.
+ *
+ * @package WordPress
+ * @subpackage Interactivity API
+ *
+ * @since 6.5.0
+ *
+ * @group interactivity-api
+ */
+class Tests_WP_Interactivity_API_WP_Text extends WP_UnitTestCase {
+	/**
+	 * Instance of WP_Interactivity_API.
+	 *
+	 * @var WP_Interactivity_API
+	 */
+	protected $interactivity;
+
+	/**
+	 * Set up.
+	 */
+	public function set_up() {
+		parent::set_up();
+		$this->interactivity = new WP_Interactivity_API();
+		$this->interactivity->state( 'myPlugin', array( 'text' => 'Updated' ) );
+	}
+
+	/**
+	 * Tests that the `data-wp-text` directive sets inner text content.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_text_sets_inner_content() {
+		$html     = '<div data-wp-text="myPlugin::state.text">Text</div>';
+		$new_html = $this->interactivity->process_directives( $html );
+		$this->assertEquals( '<div data-wp-text="myPlugin::state.text">Updated</div>', $new_html );
+	}
+
+	/**
+	 * Tests that the `data-wp-text` directive works with numerical values.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_text_sets_inner_content_numbers() {
+		$this->interactivity->state( 'myPlugin', array( 'number' => 100 ) );
+		$html     = '<div data-wp-text="myPlugin::state.number">Text</div>';
+		$new_html = $this->interactivity->process_directives( $html );
+		$this->assertEquals( '<div data-wp-text="myPlugin::state.number">100</div>', $new_html );
+	}
+
+	/**
+	 * Tests that the `data-wp-text` directive removes inner text content when the
+	 * state is not a string or number.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_text_removes_inner_content_on_types_that_are_not_strings_or_numbers() {
+		$this->interactivity->state(
+			'myPlugin',
+			array(
+				'true'  => true,
+				'false' => false,
+				'null'  => null,
+				'array' => array(),
+				'func'  => function () {},
+			)
+		);
+		$html     = '<div data-wp-text="myPlugin::state.true">Text</div>';
+		$new_html = $this->interactivity->process_directives( $html );
+		$this->assertEquals( '<div data-wp-text="myPlugin::state.true"></div>', $new_html );
+
+		$html     = '<div data-wp-text="myPlugin::state.false">Text</div>';
+		$new_html = $this->interactivity->process_directives( $html );
+		$this->assertEquals( '<div data-wp-text="myPlugin::state.false"></div>', $new_html );
+
+		$html     = '<div data-wp-text="myPlugin::state.null">Text</div>';
+		$new_html = $this->interactivity->process_directives( $html );
+		$this->assertEquals( '<div data-wp-text="myPlugin::state.null"></div>', $new_html );
+
+		$html     = '<div data-wp-text="myPlugin::state.array">Text</div>';
+		$new_html = $this->interactivity->process_directives( $html );
+		$this->assertEquals( '<div data-wp-text="myPlugin::state.array"></div>', $new_html );
+
+		$html     = '<div data-wp-text="myPlugin::state.func">Text</div>';
+		$new_html = $this->interactivity->process_directives( $html );
+		$this->assertEquals( '<div data-wp-text="myPlugin::state.func"></div>', $new_html );
+	}
+
+	/**
+	 * Tests that the `data-wp-text` directive overwrites entire inner content,
+	 * including nested tags.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_text_sets_inner_content_with_nested_tags() {
+		$html     = '<div data-wp-text="myPlugin::state.text"><div><div>Text</div><div>Another text</div></div></div>';
+		$new_html = $this->interactivity->process_directives( $html );
+		$this->assertEquals( '<div data-wp-text="myPlugin::state.text">Updated</div>', $new_html );
+	}
+
+	/**
+	 * Tests that the `data-wp-text` directive works even with unbalanced tags
+	 * when they are different tags (div -> unbalanced span).
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_text_sets_inner_content_even_with_unbalanced_but_different_tags_inside_content() {
+		$html     = '<div data-wp-text="myPlugin::state.text"><span>Text</div>';
+		$new_html = $this->interactivity->process_directives( $html );
+		$this->assertEquals( '<div data-wp-text="myPlugin::state.text">Updated</div>', $new_html );
+	}
+
+	/**
+	 * Tests that the `data-wp-text` fails to overwrite inner content if there are
+	 * unbalanced when they are the same tags (div -> unbalanced div).
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_text_fails_with_unbalanced_and_same_tags_inside_content() {
+		$html     = '<div data-wp-text="myPlugin::state.text">Text<div></div>';
+		$new_html = $this->interactivity->process_directives( $html );
+		$this->assertEquals( '<div data-wp-text="myPlugin::state.text">Text<div></div>', $new_html );
+	}
+
+	/**
+	 * Tests that the `data-wp-text` directive cannot set inner HTML content and
+	 * it will be encoded as text.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_wp_text_cant_set_inner_html_in_the_content() {
+		$this->interactivity->state( 'myPlugin', array( 'text' => '<span>Updated</span>' ) );
+		$html     = '<div data-wp-text="myPlugin::state.text">Text</div>';
+		$new_html = $this->interactivity->process_directives( $html );
+		$this->assertEquals( '<div data-wp-text="myPlugin::state.text">&lt;span&gt;Updated&lt;/span&gt;</div>', $new_html );
+	}
+}
diff --git a/tests/phpunit/tests/interactivity-api/wpInteractivityAPI.php b/tests/phpunit/tests/interactivity-api/wpInteractivityAPI.php
new file mode 100644
index 0000000000000..5e8298a77e449
--- /dev/null
+++ b/tests/phpunit/tests/interactivity-api/wpInteractivityAPI.php
@@ -0,0 +1,694 @@
+<?php
+/**
+ * Unit tests covering WP_Interactivity_API functionality.
+ *
+ * @package WordPress
+ * @subpackage Interactivity API
+ *
+ * @since 6.5.0
+ *
+ * @group interactivity-api
+ *
+ * @coversDefaultClass WP_Interactivity_API
+ */
+class Tests_WP_Interactivity_API extends WP_UnitTestCase {
+	/**
+	 * Instance of WP_Interactivity_API.
+	 *
+	 * @var WP_Interactivity_API
+	 */
+	protected $interactivity;
+
+	/**
+	 * Set up.
+	 */
+	public function set_up() {
+		parent::set_up();
+		$this->interactivity = new WP_Interactivity_API();
+	}
+
+	/**
+	 * Tests that the state and config methods return an empty array at the
+	 * beginning.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::state
+	 * @covers ::config
+	 */
+	public function test_state_and_config_should_be_empty() {
+		$this->assertEquals( array(), $this->interactivity->state( 'myPlugin' ) );
+		$this->assertEquals( array(), $this->interactivity->config( 'myPlugin' ) );
+	}
+
+	/**
+	 * Tests that the state and config methods can change the state and
+	 * configuration.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::state
+	 * @covers ::config
+	 */
+	public function test_state_and_config_can_be_changed() {
+		$state  = array(
+			'a'      => 1,
+			'b'      => 2,
+			'nested' => array( 'c' => 3 ),
+		);
+		$result = $this->interactivity->state( 'myPlugin', $state );
+		$this->assertEquals( $state, $result );
+		$result = $this->interactivity->config( 'myPlugin', $state );
+		$this->assertEquals( $state, $result );
+	}
+
+	/**
+	 * Tests that different initial states and configurations can be merged.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::state
+	 * @covers ::config
+	 */
+	public function test_state_and_config_can_be_merged() {
+		$this->interactivity->state( 'myPlugin', array( 'a' => 1 ) );
+		$this->interactivity->state( 'myPlugin', array( 'b' => 2 ) );
+		$this->interactivity->state( 'otherPlugin', array( 'c' => 3 ) );
+		$this->assertEquals(
+			array(
+				'a' => 1,
+				'b' => 2,
+			),
+			$this->interactivity->state( 'myPlugin' )
+		);
+		$this->assertEquals(
+			array( 'c' => 3 ),
+			$this->interactivity->state( 'otherPlugin' )
+		);
+
+		$this->interactivity->config( 'myPlugin', array( 'a' => 1 ) );
+		$this->interactivity->config( 'myPlugin', array( 'b' => 2 ) );
+		$this->interactivity->config( 'otherPlugin', array( 'c' => 3 ) );
+		$this->assertEquals(
+			array(
+				'a' => 1,
+				'b' => 2,
+			),
+			$this->interactivity->config( 'myPlugin' )
+		);
+		$this->assertEquals(
+			array( 'c' => 3 ),
+			$this->interactivity->config( 'otherPlugin' )
+		);  }
+
+	/**
+	 * Tests that existing keys in the initial state and configuration can be
+	 * overwritten.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::state
+	 * @covers ::config
+	 */
+	public function test_state_and_config_existing_props_can_be_overwritten() {
+		$this->interactivity->state( 'myPlugin', array( 'a' => 1 ) );
+		$this->interactivity->state( 'myPlugin', array( 'a' => 2 ) );
+		$this->assertEquals(
+			array( 'a' => 2 ),
+			$this->interactivity->state( 'myPlugin' )
+		);
+
+		$this->interactivity->config( 'myPlugin', array( 'a' => 1 ) );
+		$this->interactivity->config( 'myPlugin', array( 'a' => 2 ) );
+		$this->assertEquals(
+			array( 'a' => 2 ),
+			$this->interactivity->config( 'myPlugin' )
+		);
+	}
+
+	/**
+	 * Tests that existing indexed arrays in the initial state and configuration
+	 * are replaced, not merged.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::state
+	 * @covers ::config
+	 */
+	public function test_state_and_config_existing_indexed_arrays_are_replaced() {
+		$this->interactivity->state( 'myPlugin', array( 'a' => array( 1, 2 ) ) );
+		$this->interactivity->state( 'myPlugin', array( 'a' => array( 3, 4 ) ) );
+		$this->assertEquals(
+			array( 'a' => array( 3, 4 ) ),
+			$this->interactivity->state( 'myPlugin' )
+		);
+
+		$this->interactivity->config( 'myPlugin', array( 'a' => array( 1, 2 ) ) );
+		$this->interactivity->config( 'myPlugin', array( 'a' => array( 3, 4 ) ) );
+		$this->assertEquals(
+			array( 'a' => array( 3, 4 ) ),
+			$this->interactivity->config( 'myPlugin' )
+		);
+	}
+
+	/**
+	 * Invokes the private `print_client_interactivity` method of
+	 * WP_Interactivity_API class.
+	 *
+	 * @return array|null The content of the JSON object printed on the client-side or null if nothings was printed.
+	 */
+	private function print_client_interactivity_data() {
+		$interactivity_data_markup = get_echo( array( $this->interactivity, 'print_client_interactivity_data' ) );
+		preg_match( '/<script type="application\/json" id="wp-interactivity-data">.*?(\{.*\}).*?<\/script>/s', $interactivity_data_markup, $interactivity_data_string );
+		return isset( $interactivity_data_string[1] ) ? json_decode( $interactivity_data_string[1], true ) : null;
+	}
+
+	/**
+	 * Tests that the initial state and config are correctly printed on the
+	 * client-side.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::state
+	 * @covers ::config
+	 * @covers ::print_client_interactivity_data
+	 */
+	public function test_state_and_config_is_correctly_printed() {
+		$this->interactivity->state( 'myPlugin', array( 'a' => 1 ) );
+		$this->interactivity->state( 'otherPlugin', array( 'b' => 2 ) );
+		$this->interactivity->config( 'myPlugin', array( 'a' => 1 ) );
+		$this->interactivity->config( 'otherPlugin', array( 'b' => 2 ) );
+
+		$result = $this->print_client_interactivity_data();
+
+		$data = array(
+			'myPlugin'    => array( 'a' => 1 ),
+			'otherPlugin' => array( 'b' => 2 ),
+		);
+
+		$this->assertEquals(
+			array(
+				'state'  => $data,
+				'config' => $data,
+			),
+			$result
+		);
+	}
+
+	/**
+	 * Tests that the wp-interactivity-data script is not printed if both state
+	 * and config are empty.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::print_client_interactivity_data
+	 */
+	public function test_state_and_config_dont_print_when_empty() {
+		$result = $this->print_client_interactivity_data();
+		$this->assertNull( $result );
+	}
+
+	/**
+	 * Tests that the config is not printed if it's empty.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::state
+	 * @covers ::print_client_interactivity_data
+	 */
+	public function test_config_not_printed_when_empty() {
+		$this->interactivity->state( 'myPlugin', array( 'a' => 1 ) );
+		$result = $this->print_client_interactivity_data();
+		$this->assertEquals( array( 'state' => array( 'myPlugin' => array( 'a' => 1 ) ) ), $result );
+	}
+
+	/**
+	 * Tests that the state is not printed if it's empty.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::config
+	 * @covers ::print_client_interactivity_data
+	 */
+	public function test_state_not_printed_when_empty() {
+		$this->interactivity->config( 'myPlugin', array( 'a' => 1 ) );
+		$result = $this->print_client_interactivity_data();
+		$this->assertEquals( array( 'config' => array( 'myPlugin' => array( 'a' => 1 ) ) ), $result );
+	}
+
+
+
+	/**
+	 * Tests that special characters in the initial state and configuration are
+	 * properly escaped.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::state
+	 * @covers ::config
+	 * @covers ::print_client_interactivity_data
+	 */
+	public function test_state_and_config_escape_special_characters() {
+		$this->interactivity->state( 'myPlugin', array( 'amps' => 'http://site.test/?foo=1&baz=2' ) );
+		$this->interactivity->config( 'myPlugin', array( 'tags' => 'Tags: <!-- <script>' ) );
+
+		$interactivity_data_markup = get_echo( array( $this->interactivity, 'print_client_interactivity_data' ) );
+		preg_match( '/<script type="application\/json" id="wp-interactivity-data">.*?(\{.*\}).*?<\/script>/s', $interactivity_data_markup, $interactivity_data_string );
+
+		$this->assertEquals(
+			'{"config":{"myPlugin":{"tags":"Tags: \u003C!-- \u003Cscript\u003E"}},"state":{"myPlugin":{"amps":"http:\/\/site.test\/?foo=1\u0026baz=2"}}}',
+			$interactivity_data_string[1]
+		);
+	}
+
+	/**
+	 * Tests extracting directive values from different string formats.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::extract_directive_value
+	 */
+	public function test_extract_directive_value() {
+		$extract_directive_value = new ReflectionMethod( $this->interactivity, 'extract_directive_value' );
+		$extract_directive_value->setAccessible( true );
+
+		$result = $extract_directive_value->invoke( $this->interactivity, 'state.foo', 'myPlugin' );
+		$this->assertEquals( array( 'myPlugin', 'state.foo' ), $result );
+
+		$result = $extract_directive_value->invoke( $this->interactivity, 'otherPlugin::state.foo', 'myPlugin' );
+		$this->assertEquals( array( 'otherPlugin', 'state.foo' ), $result );
+
+		$result = $extract_directive_value->invoke( $this->interactivity, '{ "isOpen": false }', 'myPlugin' );
+		$this->assertEquals( array( 'myPlugin', array( 'isOpen' => false ) ), $result );
+
+		$result = $extract_directive_value->invoke( $this->interactivity, 'otherPlugin::{ "isOpen": false }', 'myPlugin' );
+		$this->assertEquals( array( 'otherPlugin', array( 'isOpen' => false ) ), $result );
+
+		$result = $extract_directive_value->invoke( $this->interactivity, 'true', 'myPlugin' );
+		$this->assertEquals( array( 'myPlugin', true ), $result );
+
+		$result = $extract_directive_value->invoke( $this->interactivity, 'false', 'myPlugin' );
+		$this->assertEquals( array( 'myPlugin', false ), $result );
+
+		$result = $extract_directive_value->invoke( $this->interactivity, 'null', 'myPlugin' );
+		$this->assertEquals( array( 'myPlugin', null ), $result );
+
+		$result = $extract_directive_value->invoke( $this->interactivity, '100', 'myPlugin' );
+		$this->assertEquals( array( 'myPlugin', 100 ), $result );
+
+		$result = $extract_directive_value->invoke( $this->interactivity, '1.2', 'myPlugin' );
+		$this->assertEquals( array( 'myPlugin', 1.2 ), $result );
+
+		$result = $extract_directive_value->invoke( $this->interactivity, '1.2.3', 'myPlugin' );
+		$this->assertEquals( array( 'myPlugin', '1.2.3' ), $result );
+
+		$result = $extract_directive_value->invoke( $this->interactivity, 'otherPlugin::true', 'myPlugin' );
+		$this->assertEquals( array( 'otherPlugin', true ), $result );
+
+		$result = $extract_directive_value->invoke( $this->interactivity, 'otherPlugin::false', 'myPlugin' );
+		$this->assertEquals( array( 'otherPlugin', false ), $result );
+
+		$result = $extract_directive_value->invoke( $this->interactivity, 'otherPlugin::null', 'myPlugin' );
+		$this->assertEquals( array( 'otherPlugin', null ), $result );
+
+		$result = $extract_directive_value->invoke( $this->interactivity, 'otherPlugin::100', 'myPlugin' );
+		$this->assertEquals( array( 'otherPlugin', 100 ), $result );
+
+		$result = $extract_directive_value->invoke( $this->interactivity, 'otherPlugin::1.2', 'myPlugin' );
+		$this->assertEquals( array( 'otherPlugin', 1.2 ), $result );
+
+		$result = $extract_directive_value->invoke( $this->interactivity, 'otherPlugin::1.2.3', 'myPlugin' );
+		$this->assertEquals( array( 'otherPlugin', '1.2.3' ), $result );
+
+		$result = $extract_directive_value->invoke( $this->interactivity, 'otherPlugin::[{"o":4}, null, 3e6]', 'myPlugin' );
+		$this->assertEquals( array( 'otherPlugin', array( array( 'o' => 4 ), null, 3000000.0 ) ), $result );
+	}
+
+	/**
+	 * Tests extracting directive values with empty or invalid input.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::extract_directive_value
+	 */
+	public function test_extract_directive_value_empty_values() {
+		$extract_directive_value = new ReflectionMethod( $this->interactivity, 'extract_directive_value' );
+		$extract_directive_value->setAccessible( true );
+
+		$result = $extract_directive_value->invoke( $this->interactivity, '', 'myPlugin' );
+		$this->assertEquals( array( 'myPlugin', null ), $result );
+
+		// This is a boolean attribute.
+		$result = $extract_directive_value->invoke( $this->interactivity, true, 'myPlugin' );
+		$this->assertEquals( array( 'myPlugin', null ), $result );
+
+		$result = $extract_directive_value->invoke( $this->interactivity, false, 'myPlugin' );
+		$this->assertEquals( array( 'myPlugin', null ), $result );
+
+		$result = $extract_directive_value->invoke( $this->interactivity, null, 'myPlugin' );
+		$this->assertEquals( array( 'myPlugin', null ), $result );
+
+		// A string ending in `::` without any extra characters is not considered a
+		// namespace.
+		$result = $extract_directive_value->invoke( $this->interactivity, 'myPlugin::', 'myPlugin' );
+		$this->assertEquals( array( 'myPlugin', 'myPlugin::' ), $result );
+
+		// A namespace with invalid characters is not considered a valid namespace.
+		$result = $extract_directive_value->invoke( $this->interactivity, '$myPlugin::state.foo', 'myPlugin' );
+		$this->assertEquals( array( 'myPlugin', '$myPlugin::state.foo' ), $result );
+	}
+
+	/**
+	 * Tests extracting directive values from invalid JSON strings.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::extract_directive_value
+	 */
+	public function test_extract_directive_value_invalid_json() {
+		$extract_directive_value = new ReflectionMethod( $this->interactivity, 'extract_directive_value' );
+		$extract_directive_value->setAccessible( true );
+
+		// Invalid JSON due to missing quotes. Returns the original value.
+		$result = $extract_directive_value->invoke( $this->interactivity, '{ isOpen: false }', 'myPlugin' );
+		$this->assertEquals( array( 'myPlugin', '{ isOpen: false }' ), $result );
+
+		// Null string. Returns null.
+		$result = $extract_directive_value->invoke( $this->interactivity, 'null', 'myPlugin' );
+		$this->assertEquals( array( 'myPlugin', null ), $result );
+	}
+
+	/**
+	 * Tests the ability to extract prefix and suffix from a directive attribute
+	 * name.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::extract_prefix_and_suffix
+	 */
+	public function test_extract_prefix_and_suffix() {
+		$extract_prefix_and_suffix = new ReflectionMethod( $this->interactivity, 'extract_prefix_and_suffix' );
+		$extract_prefix_and_suffix->setAccessible( true );
+
+		$result = $extract_prefix_and_suffix->invoke( $this->interactivity, 'data-wp-interactive' );
+		$this->assertEquals( array( 'data-wp-interactive' ), $result );
+
+		$result = $extract_prefix_and_suffix->invoke( $this->interactivity, 'data-wp-bind--src' );
+		$this->assertEquals( array( 'data-wp-bind', 'src' ), $result );
+
+		$result = $extract_prefix_and_suffix->invoke( $this->interactivity, 'data-wp-foo--and--bar' );
+		$this->assertEquals( array( 'data-wp-foo', 'and--bar' ), $result );
+	}
+
+	/**
+	 * Tests that the `process_directives` method doesn't change the HTML if it
+	 * doesn't contain directives.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_process_directives_do_nothing_without_directives() {
+		$html           = '<div>Inner content here</div>';
+		$processed_html = $this->interactivity->process_directives( $html );
+		$this->assertEquals( $html, $processed_html );
+
+		$html           = '<div><span>Content</span><strong>More Content</strong></div>';
+		$processed_html = $this->interactivity->process_directives( $html );
+		$this->assertEquals( $html, $processed_html );
+	}
+
+	/**
+	 * Tests that the `process_directives` method changes the HTML if it contains
+	 * directives.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_process_directives_changes_html_with_balanced_tags() {
+		$this->interactivity->state( 'myPlugin', array( 'id' => 'some-id' ) );
+		$html           = '<div data-wp-bind--id="myPlugin::state.id">Inner content</div>';
+		$processed_html = $this->interactivity->process_directives( $html );
+		$p              = new WP_HTML_Tag_Processor( $processed_html );
+		$p->next_tag();
+		$this->assertEquals( 'some-id', $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests how `process_directives` handles HTML with unknown directives.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_process_directives_doesnt_fail_with_unknown_directives() {
+		$html           = '<div data-wp-uknown="">Text</div>';
+		$processed_html = $this->interactivity->process_directives( $html );
+		$this->assertEquals( $html, $processed_html );
+	}
+
+	/**
+	 * Tests that directives are processed in the correct order.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_process_directives_process_the_directives_in_the_correct_order() {
+		$html           = '
+			<div
+				data-wp-interactive=\'{ "namespace": "test" }\'
+				data-wp-context=\'{ "isClass": true, "id": "some-id", "text": "Updated", "display": "none" }\'
+				data-wp-bind--id="context.id"
+				data-wp-class--some-class="context.isClass"
+				data-wp-style--display="context.display"
+				data-wp-text="context.text"
+			>Text</div>';
+		$processed_html = $this->interactivity->process_directives( $html );
+		$p              = new WP_HTML_Tag_Processor( $processed_html );
+		$p->next_tag();
+		$this->assertEquals( 'some-id', $p->get_attribute( 'id' ) );
+		$this->assertEquals( 'some-class', $p->get_attribute( 'class' ) );
+		$this->assertEquals( 'display:none;', $p->get_attribute( 'style' ) );
+		$this->assertStringContainsString( 'Updated', $p->get_updated_html() );
+		$this->assertStringNotContainsString( 'Text', $p->get_updated_html() );
+	}
+
+	/**
+	 * Tests that the `process_directives` returns the same HTML if it contains
+	 * unbalanced tags.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_process_directives_doesnt_change_html_if_contains_unbalanced_tags() {
+		$this->interactivity->state( 'myPlugin', array( 'id' => 'some-id' ) );
+
+		$html_samples = array(
+			'<div data-wp-bind--id="myPlugin::state.id">Inner content</div></div>',
+			'<div data-wp-bind--id="myPlugin::state.id">Inner content</div><div>',
+			'<div><div data-wp-bind--id="myPlugin::state.id">Inner content</div>',
+			'</div><div data-wp-bind--id="myPlugin::state.id">Inner content</div>',
+			'<div data-wp-bind--id="myPlugin::state.id">Inner<div>content</div>',
+			'<div data-wp-bind--id="myPlugin::state.id">Inner</div>content</div>',
+			'<div data-wp-bind--id="myPlugin::state.id"><span>Inner content</div>',
+			'<div data-wp-bind--id="myPlugin::state.id">Inner content</div></span>',
+			'<div data-wp-bind--id="myPlugin::state.id"><span>Inner content</div></span>',
+			'<div data-wp-bind--id="myPlugin::state.id">Inner conntent</ ></div>',
+		);
+
+		foreach ( $html_samples as $html ) {
+			$processed_html = $this->interactivity->process_directives( $html );
+			$p              = new WP_HTML_Tag_Processor( $processed_html );
+			$p->next_tag();
+			$this->assertNull( $p->get_attribute( 'id' ) );
+		}
+	}
+
+	/**
+	 * Tests that the `process_directives` returns the same HTML if it finds an
+	 * SVG tag.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_process_directives_doesnt_change_html_if_contains_svgs() {
+		$this->interactivity->state( 'myPlugin', array( 'id' => 'some-id' ) );
+		$html           = '
+			<div data-wp-bind--id="myPlugin::state.id">
+				<svg height="100" width="100">
+					<circle cx="50" cy="50" r="40" stroke="black" stroke-width="3" fill="red" />
+				</svg> 
+			</div>
+		';
+		$processed_html = $this->interactivity->process_directives( $html );
+		$p              = new WP_HTML_Tag_Processor( $processed_html );
+		$p->next_tag();
+		$this->assertNull( $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Tests that the `process_directives` returns the same HTML if it finds an
+	 * MathML tag.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::process_directives
+	 */
+	public function test_process_directives_doesnt_change_html_if_contains_math() {
+		$this->interactivity->state( 'myPlugin', array( 'id' => 'some-id' ) );
+		$html           = '
+			<div data-wp-bind--id="myPlugin::state.id">
+				<math>
+					<mi>x</mi>
+					<mo>=</mo>
+					<mi>1</mi>
+				</math>
+			</div>
+		';
+		$processed_html = $this->interactivity->process_directives( $html );
+		$p              = new WP_HTML_Tag_Processor( $processed_html );
+		$p->next_tag();
+		$this->assertNull( $p->get_attribute( 'id' ) );
+	}
+
+	/**
+	 * Invokes the private `evaluate` method of WP_Interactivity_API class.
+	 *
+	 * @param string $directive_value The directive attribute value to evaluate.
+	 * @return mixed The result of the evaluate method.
+	 */
+	private function evaluate( $directive_value ) {
+		$generate_state = function ( $name ) {
+			return array(
+				'key'    => $name,
+				'nested' => array( 'key' => $name . '-nested' ),
+			);
+		};
+		$this->interactivity->state( 'myPlugin', $generate_state( 'myPlugin-state' ) );
+		$this->interactivity->state( 'otherPlugin', $generate_state( 'otherPlugin-state' ) );
+		$context  = array(
+			'myPlugin'    => $generate_state( 'myPlugin-context' ),
+			'otherPlugin' => $generate_state( 'otherPlugin-context' ),
+		);
+		$evaluate = new ReflectionMethod( $this->interactivity, 'evaluate' );
+		$evaluate->setAccessible( true );
+		return $evaluate->invokeArgs( $this->interactivity, array( $directive_value, 'myPlugin', $context ) );
+	}
+
+	/**
+	 * Tests that the `evaluate` method operates correctly for valid expressions.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::evaluate
+	 */
+	public function test_evaluate_value() {
+		$result = $this->evaluate( 'state.key' );
+		$this->assertEquals( 'myPlugin-state', $result );
+
+		$result = $this->evaluate( 'context.key' );
+		$this->assertEquals( 'myPlugin-context', $result );
+
+		$result = $this->evaluate( 'otherPlugin::state.key' );
+		$this->assertEquals( 'otherPlugin-state', $result );
+
+		$result = $this->evaluate( 'otherPlugin::context.key' );
+		$this->assertEquals( 'otherPlugin-context', $result );
+	}
+
+	/**
+	 * Tests that the `evaluate` method operates correctly when used with the
+	 * negation operator (!).
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::evaluate
+	 */
+	public function test_evaluate_value_negation() {
+		$result = $this->evaluate( '!state.key' );
+		$this->assertFalse( $result );
+
+		$result = $this->evaluate( '!context.key' );
+		$this->assertFalse( $result );
+
+		$result = $this->evaluate( 'otherPlugin::!state.key' );
+		$this->assertFalse( $result );
+
+		$result = $this->evaluate( 'otherPlugin::!context.key' );
+		$this->assertFalse( $result );
+	}
+
+	/**
+	 * Tests the `evaluate` method with non-existent paths.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::evaluate
+	 */
+	public function test_evaluate_non_existent_path() {
+		$result = $this->evaluate( 'state.nonExistentKey' );
+		$this->assertNull( $result );
+
+		$result = $this->evaluate( 'context.nonExistentKey' );
+		$this->assertNull( $result );
+
+		$result = $this->evaluate( 'otherPlugin::state.nonExistentKey' );
+		$this->assertNull( $result );
+
+		$result = $this->evaluate( 'otherPlugin::context.nonExistentKey' );
+		$this->assertNull( $result );
+
+		$result = $this->evaluate( ' state.key' ); // Extra space.
+		$this->assertNull( $result );
+
+		$result = $this->evaluate( 'otherPlugin:: state.key' ); // Extra space.
+		$this->assertNull( $result );
+	}
+
+	/**
+	 * Tests the `evaluate` method for retrieving nested values.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::evaluate
+	 */
+	public function test_evaluate_nested_value() {
+		$result = $this->evaluate( 'state.nested.key' );
+		$this->assertEquals( 'myPlugin-state-nested', $result );
+
+		$result = $this->evaluate( 'context.nested.key' );
+		$this->assertEquals( 'myPlugin-context-nested', $result );
+
+		$result = $this->evaluate( 'otherPlugin::state.nested.key' );
+		$this->assertEquals( 'otherPlugin-state-nested', $result );
+
+		$result = $this->evaluate( 'otherPlugin::context.nested.key' );
+		$this->assertEquals( 'otherPlugin-context-nested', $result );
+	}
+
+	/**
+	 * Tests the `kebab_to_camel_case` method.
+	 *
+	 * @covers ::kebab_to_camel_case
+	 */
+	public function test_kebab_to_camel_case() {
+		$method = new ReflectionMethod( $this->interactivity, 'kebab_to_camel_case' );
+		$method->setAccessible( true );
+
+		$this->assertSame( '', $method->invoke( $this->interactivity, '' ) );
+		$this->assertSame( 'item', $method->invoke( $this->interactivity, 'item' ) );
+		$this->assertSame( 'myItem', $method->invoke( $this->interactivity, 'my-item' ) );
+		$this->assertSame( 'my_item', $method->invoke( $this->interactivity, 'my_item' ) );
+		$this->assertSame( 'myItem', $method->invoke( $this->interactivity, 'My-iTem' ) );
+		$this->assertSame( 'myItemWithMultipleHyphens', $method->invoke( $this->interactivity, 'my-item-with-multiple-hyphens' ) );
+		$this->assertSame( 'myItemWith-DoubleHyphens', $method->invoke( $this->interactivity, 'my-item-with--double-hyphens' ) );
+		$this->assertSame( 'myItemWith_underScore', $method->invoke( $this->interactivity, 'my-item-with_under-score' ) );
+		$this->assertSame( 'myItem', $method->invoke( $this->interactivity, '-my-item' ) );
+		$this->assertSame( 'myItem', $method->invoke( $this->interactivity, 'my-item-' ) );
+		$this->assertSame( 'myItem', $method->invoke( $this->interactivity, '-my-item-' ) );
+	}
+}
diff --git a/tests/phpunit/tests/interactivity-api/wpInteractivityAPIDirectivesProcessor.php b/tests/phpunit/tests/interactivity-api/wpInteractivityAPIDirectivesProcessor.php
new file mode 100644
index 0000000000000..bf2225597c0ae
--- /dev/null
+++ b/tests/phpunit/tests/interactivity-api/wpInteractivityAPIDirectivesProcessor.php
@@ -0,0 +1,781 @@
+<?php
+/**
+ * Unit tests covering WP_Interactivity_API_Directives_Processor functionality.
+ *
+ * @package WordPress
+ * @subpackage Interactivity API
+ *
+ * @since 6.5.0
+ *
+ * @group interactivity-api
+ *
+ * @coversDefaultClass WP_Interactivity_API_Directives_Processor
+ */
+class Tests_WP_Interactivity_API_Directives_Processor extends WP_UnitTestCase {
+	/**
+	 * Tests the `get_content_between_balanced_template_tags` method on template
+	 * tags.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::get_content_between_balanced_template_tags
+	 */
+	public function test_get_content_between_balanced_template_tags_standard_tags() {
+		$content = '<template>Text</template>';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$this->assertEquals( 'Text', $p->get_content_between_balanced_template_tags() );
+
+		$content = '<template>Text</template><template>More text</template>';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$this->assertEquals( 'Text', $p->get_content_between_balanced_template_tags() );
+		$p->next_tag();
+		$this->assertEquals( 'More text', $p->get_content_between_balanced_template_tags() );
+	}
+
+	/**
+	 * Tests the `get_content_between_balanced_template_tags` method on an empty
+	 * tag.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::get_content_between_balanced_template_tags
+	 */
+	public function test_get_content_between_balanced_template_tags_empty_tag() {
+		$content = '<template></template>';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$this->assertEquals( '', $p->get_content_between_balanced_template_tags() );
+	}
+
+	/**
+	 * Tests the `get_content_between_balanced_template_tags` method with
+	 * non-template tags.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::get_content_between_balanced_template_tags
+	 */
+	public function test_get_content_between_balanced_template_tags_self_closing_tag() {
+		$content = '<img src="example.jpg">';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$this->assertNull( $p->get_content_between_balanced_template_tags() );
+
+		$content = '<div>Text</div>';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$this->assertNull( $p->get_content_between_balanced_template_tags() );
+	}
+
+	/**
+	 * Tests the `get_content_between_balanced_template_tags` method with nested
+	 * template tags.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::get_content_between_balanced_template_tags
+	 */
+	public function test_get_content_between_balanced_template_tags_nested_tags() {
+		$content = '<template><span>Content</span><strong>More Content</strong></template>';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$this->assertEquals( '<span>Content</span><strong>More Content</strong>', $p->get_content_between_balanced_template_tags() );
+
+		$content = '<template><template>Content</template><img src="example.jpg"></template>';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$this->assertEquals( '<template>Content</template><img src="example.jpg">', $p->get_content_between_balanced_template_tags() );
+	}
+
+	/**
+	 * Tests the `get_content_between_balanced_template_tags` method when no tags
+	 * are present.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::get_content_between_balanced_template_tags
+	 */
+	public function test_get_content_between_balanced_template_tags_no_tags() {
+		$content = 'Just a string with no tags.';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$this->assertNull( $p->get_content_between_balanced_template_tags() );
+	}
+
+	/**
+	 * Tests the `get_content_between_balanced_template_tags` method with unbalanced tags.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::get_content_between_balanced_template_tags
+	 */
+	public function test_get_content_between_balanced_template_tags_with_unbalanced_tags() {
+		$content = '<template>Missing closing template';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$this->assertNull( $p->get_content_between_balanced_template_tags() );
+
+		$content = '<template><template>Missing closing template</template>';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$this->assertNull( $p->get_content_between_balanced_template_tags() );
+
+		$content = '<template>Missing closing template</span>';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$this->assertNull( $p->get_content_between_balanced_template_tags() );
+
+		// It supports unbalanced tags inside the content.
+		$content = '<template>Missing opening span</span></template>';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$this->assertEquals( 'Missing opening span</span>', $p->get_content_between_balanced_template_tags() );
+	}
+
+	/**
+	 * Tests the `get_content_between_balanced_template_tags` method when called
+	 * on a closer tag.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::get_content_between_balanced_template_tags
+	 */
+	public function test_get_content_between_balanced_template_tags_on_closing_tag() {
+		$content = '<template>Text</template>';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag( array( 'tag_closers' => 'visit' ) );
+		$p->next_tag( array( 'tag_closers' => 'visit' ) );
+		$this->assertNull( $p->get_content_between_balanced_template_tags() );
+	}
+
+	/**
+	 * Tests the `get_content_between_balanced_template_tags` method positions the
+	 * cursor on the closer tag.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::get_content_between_balanced_template_tags
+	 */
+	public function test_get_content_between_balanced_template_tags_positions_cursor_on_closer_tag() {
+		$content = '<template>Text</template><div>More text</div>';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$p->get_content_between_balanced_template_tags();
+		$this->assertEquals( 'TEMPLATE', $p->get_tag() );
+		$this->assertTrue( $p->is_tag_closer() );
+		$p->next_tag();
+		$this->assertEquals( 'DIV', $p->get_tag() );
+	}
+
+	/**
+	 * Tests the `set_content_between_balanced_tags` method on standard tags.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::set_content_between_balanced_tags
+	 */
+	public function test_set_content_between_balanced_tags_standard_tags() {
+		$content = '<div>Text</div>';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$result = $p->set_content_between_balanced_tags( 'New text' );
+		$this->assertTrue( $result );
+		$this->assertEquals( '<div>New text</div>', $p );
+
+		$content = '<div>Text</div><div>More text</div>';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$result = $p->set_content_between_balanced_tags( 'New text' );
+		$this->assertTrue( $result );
+		$this->assertEquals( '<div>New text</div><div>More text</div>', $p );
+		$p->next_tag();
+		$result = $p->set_content_between_balanced_tags( 'More new text' );
+		$this->assertTrue( $result );
+		$this->assertEquals( '<div>New text</div><div>More new text</div>', $p );
+	}
+
+	/**
+	 * Tests the `set_content_between_balanced_tags` method when called on a
+	 * closing tag.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::set_content_between_balanced_tags
+	 */
+	public function test_set_content_between_balanced_tags_on_closing_tag() {
+		$content = '<div>Text</div>';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag( array( 'tag_closers' => 'visit' ) );
+		$p->next_tag( array( 'tag_closers' => 'visit' ) );
+		$result = $p->set_content_between_balanced_tags( 'New text' );
+		$this->assertFalse( $result );
+		$this->assertEquals( '<div>Text</div>', $p );
+	}
+
+	/**
+	 * Tests the `set_content_between_balanced_tags` method on multiple calls to
+	 * the same tag.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::set_content_between_balanced_tags
+	 */
+	public function test_set_content_between_balanced_tags_multiple_calls_in_same_tag() {
+		$content = '<div>Text</div>';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$result = $p->set_content_between_balanced_tags( 'New text' );
+		$this->assertTrue( $result );
+		$this->assertEquals( '<div>New text</div>', $p );
+		$result = $p->set_content_between_balanced_tags( 'More text' );
+		$this->assertTrue( $result );
+		$this->assertEquals( '<div>More text</div>', $p );
+	}
+
+	/**
+	 * Tests the `set_content_between_balanced_tags` method on combinations with
+	 * set_attribute calls.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::set_content_between_balanced_tags
+	 */
+	public function test_set_content_between_balanced_tags_with_set_attribute() {
+		$content = '<div>Text</div>';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$p->set_attribute( 'class', 'test' );
+		$result = $p->set_content_between_balanced_tags( 'New text' );
+		$this->assertTrue( $result );
+		$this->assertEquals( '<div class="test">New text</div>', $p );
+
+		$content = '<div>Text</div>';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$result = $p->set_content_between_balanced_tags( 'New text' );
+		$this->assertTrue( $result );
+		$p->set_attribute( 'class', 'test' );
+		$this->assertEquals( '<div class="test">New text</div>', $p );
+	}
+
+	/**
+	 * Tests the `set_content_between_balanced_tags` method where the existing
+	 * content includes tags.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::set_content_between_balanced_tags
+	 */
+	public function test_set_content_between_balanced_tags_with_existing_tags() {
+		$content = '<div><span>Text</span></div>';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$result = $p->set_content_between_balanced_tags( 'New text' );
+		$this->assertTrue( $result );
+		$this->assertEquals( '<div>New text</div>', $p );
+	}
+
+	/**
+	 * Tests the `set_content_between_balanced_tags` method where the new content
+	 * includes tags.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::set_content_between_balanced_tags
+	 */
+	public function test_set_content_between_balanced_tags_with_new_tags() {
+		$content     = '<div>Text</div>';
+		$new_content = '<span>New text</span><a href="#">Link</a>';
+		$p           = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$p->set_content_between_balanced_tags( $new_content );
+		$this->assertEquals( '<div>&lt;span&gt;New text&lt;/span&gt;&lt;a href=&quot;#&quot;&gt;Link&lt;/a&gt;</div>', $p );
+	}
+
+	/**
+	 * Tests the `set_content_between_balanced_tags` method with an empty string.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::set_content_between_balanced_tags
+	 */
+	public function test_set_content_between_balanced_tags_empty() {
+		$content = '<div>Text</div>';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$result = $p->set_content_between_balanced_tags( '' );
+		$this->assertTrue( $result );
+		$this->assertEquals( '<div></div>', $p );
+
+		$content = '<div><div>Text</div></div>';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$result = $p->set_content_between_balanced_tags( '' );
+		$this->assertTrue( $result );
+		$this->assertEquals( '<div></div>', $p );
+	}
+
+	/**
+	 * Tests the `set_content_between_balanced_tags` method on self-closing tags.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::set_content_between_balanced_tags
+	 */
+	public function test_set_content_between_balanced_tags_self_closing_tag() {
+		$content = '<img src="example.jpg">';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$result = $p->set_content_between_balanced_tags( 'New text' );
+		$this->assertFalse( $result );
+		$this->assertEquals( $content, $p );
+	}
+
+	/**
+	 * Tests the `set_content_between_balanced_tags` method on a non-existent tag.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::set_content_between_balanced_tags
+	 */
+	public function test_set_content_between_balanced_tags_non_existent_tag() {
+		$content = 'Just a string with no tags.';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$result = $p->set_content_between_balanced_tags( 'New text' );
+		$this->assertFalse( $result );
+		$this->assertEquals( $content, $p );
+	}
+
+	/**
+	 * Tests the `set_content_between_balanced_tags` method with unbalanced tags.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::set_content_between_balanced_tags
+	 */
+	public function test_set_content_between_balanced_tags_with_unbalanced_tags() {
+		$new_content = 'New text';
+
+		$content = '<div>Missing closing div';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$result = $p->set_content_between_balanced_tags( $new_content );
+		$this->assertFalse( $result );
+		$this->assertEquals( $content, $p );
+
+		$content = '<div><div>Missing closing div</div>';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$result = $p->set_content_between_balanced_tags( $new_content );
+		$this->assertFalse( $result );
+		$this->assertEquals( $content, $p );
+
+		$content = '<div>Missing closing div</span>';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$result = $p->set_content_between_balanced_tags( $new_content );
+		$this->assertFalse( $result );
+		$this->assertEquals( $content, $p );
+
+		// It supports unbalanced tags inside the content.
+		$content = '<div>Missing opening span</span></div>';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$result = $p->set_content_between_balanced_tags( $new_content );
+		$this->assertTrue( $result );
+		$this->assertEquals( '<div>New text</div>', $p );
+	}
+
+	/**
+	 * Tests the `has_and_visits_its_closer_tag` method.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::has_and_visits_its_closer_tag
+	 */
+	public function test_has_and_visits_its_closer_tag() {
+		$void_tags = array( 'area', 'base', 'br', 'col', 'embed', 'hr', 'img', 'input', 'link', 'meta', 'source', 'track', 'wbr' );
+		foreach ( $void_tags as $tag_name ) {
+			$content = "<{$tag_name} id={$tag_name}>";
+			$p       = new WP_Interactivity_API_Directives_Processor( $content );
+			$p->next_tag();
+			$this->assertFalse( $p->has_and_visits_its_closer_tag() );
+		}
+
+		$tags_that_dont_visit_closing_tag = array( 'script', 'iframe', 'textarea', 'iframe', 'style' );
+		foreach ( $tags_that_dont_visit_closing_tag as $tag_name ) {
+			$content = "<{$tag_name} id={$tag_name}>Some content</{$tag_name}>";
+			$p       = new WP_Interactivity_API_Directives_Processor( $content );
+			$p->next_tag();
+			$this->assertFalse( $p->has_and_visits_its_closer_tag() );
+		}
+
+		$tags_that_visit_closing_tag = array( 'div', 'span', 'p', 'h1', 'main' );
+		foreach ( $tags_that_visit_closing_tag as $tag_name ) {
+			$content = "<{$tag_name} id={$tag_name}>Some content</{$tag_name}>";
+			$p       = new WP_Interactivity_API_Directives_Processor( $content );
+			$p->next_tag();
+			$this->assertTrue( $p->has_and_visits_its_closer_tag() );
+		}
+
+		// Test an upercase tag.
+		$content = '<IMG src="example.jpg">';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$this->assertFalse( $p->has_and_visits_its_closer_tag() );
+
+		// Test an empty string.
+		$content = '';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$this->assertFalse( $p->has_and_visits_its_closer_tag() );
+
+		// Test on text nodes.
+		$content = 'This is just some text';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$this->assertFalse( $p->has_and_visits_its_closer_tag() );
+	}
+
+	/**
+	 * Tests the `append_content_after_template_tag_closer` method with a simple
+	 * text.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::append_content_after_template_tag_closer
+	 */
+	public function test_append_content_after_template_tag_closer_simple_text() {
+		$content_1 = '<template>Text</template>';
+		$content_2 = 'New text';
+		$p         = new WP_Interactivity_API_Directives_Processor( $content_1 );
+		$p->next_tag( array( 'tag_closers' => 'visit' ) );
+		$p->next_tag( array( 'tag_closers' => 'visit' ) );
+		$result = $p->append_content_after_template_tag_closer( $content_2 );
+		$this->assertTrue( $result );
+		$this->assertEquals( $content_1 . $content_2, $p );
+		$this->assertFalse( $p->next_tag() ); // There are no more tags.
+	}
+
+	/**
+	 * Tests the `append_content_after_template_tag_closer` method with simple
+	 * tags.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::append_content_after_template_tag_closer
+	 */
+	public function test_append_content_after_template_tag_closer_simple_tags() {
+		$content_1 = '<template>Text</template>';
+		$content_2 = '<template class="content-2">New text</template>';
+		$content_3 = '<template class="content-3">More new text</template>';
+		$p         = new WP_Interactivity_API_Directives_Processor( $content_1 );
+		$p->next_tag( array( 'tag_closers' => 'visit' ) );
+		$p->next_tag( array( 'tag_closers' => 'visit' ) );
+		$result = $p->append_content_after_template_tag_closer( $content_2 );
+		$this->assertTrue( $result );
+		$this->assertEquals( $content_1 . $content_2, $p );
+		$p->next_tag( array( 'tag_closers' => 'visit' ) );
+		$this->assertEquals( 'content-2', $p->get_attribute( 'class' ) );
+		$p->next_tag( array( 'tag_closers' => 'visit' ) );
+		$result = $p->append_content_after_template_tag_closer( $content_3 );
+		$this->assertTrue( $result );
+		$p->next_tag( array( 'tag_closers' => 'visit' ) );
+		$this->assertEquals( $content_1 . $content_2 . $content_3, $p );
+		$this->assertEquals( 'content-3', $p->get_attribute( 'class' ) );
+	}
+
+	/**
+	 * Tests the `append_content_after_template_tag_closer` method in the middle
+	 * of two tags.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::append_content_after_template_tag_closer
+	 */
+	public function test_append_content_after_template_tag_closer_in_the_middle_of_tags() {
+		$content_1 = '<template>Text</template>';
+		$content_2 = 'New text';
+		$content_3 = '<template class="content-3">More new text</template>';
+		$content_4 = '<template class="content-4">Even more new text</template>';
+
+		$p = new WP_Interactivity_API_Directives_Processor( $content_1 . $content_3 );
+		$p->next_tag( array( 'tag_closers' => 'visit' ) );
+		$p->next_tag( array( 'tag_closers' => 'visit' ) );
+		$result = $p->append_content_after_template_tag_closer( $content_2 );
+		$this->assertTrue( $result );
+		$this->assertEquals( $content_1 . $content_2 . $content_3, $p );
+		$p->next_tag( array( 'tag_closers' => 'visit' ) );
+		$this->assertEquals( 'content-3', $p->get_attribute( 'class' ) );
+
+		$p = new WP_Interactivity_API_Directives_Processor( $content_1 . $content_3 );
+		$p->next_tag( array( 'tag_closers' => 'visit' ) );
+		$p->next_tag( array( 'tag_closers' => 'visit' ) );
+		$result = $p->append_content_after_template_tag_closer( $content_4 );
+		$this->assertTrue( $result );
+		$this->assertEquals( $content_1 . $content_4 . $content_3, $p );
+		$p->next_tag( array( 'tag_closers' => 'visit' ) );
+		$this->assertEquals( 'content-4', $p->get_attribute( 'class' ) );
+	}
+
+	/**
+	 * Tests the `append_content_after_template_tag_closer` method doesn't modify
+	 * the content when called on an opener tag.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::append_content_after_template_tag_closer
+	 */
+	public function test_append_content_after_template_tag_closer_on_opener_tag() {
+		$content = '<template>Text</template>';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag( array( 'tag_closers' => 'visit' ) );
+		$result = $p->append_content_after_template_tag_closer( 'New text' );
+		$this->assertFalse( $result );
+		$this->assertEquals( $content, $p );
+	}
+
+	/**
+	 * Tests the `append_content_after_template_tag_closer` method on multiple
+	 * calls to the same tag.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::append_content_after_template_tag_closer
+	 */
+	public function test_append_content_after_template_tag_closer_multiple_calls_in_same_tag() {
+		$content_1 = '<template class="content-1">Text</template>';
+		$content_2 = '<template class="content-2">New text</template>';
+		$content_3 = '<template class="content-3">More new text</template>';
+		$p         = new WP_Interactivity_API_Directives_Processor( $content_1 );
+		$p->next_tag( array( 'tag_closers' => 'visit' ) );
+		$p->set_bookmark( 'first template' );
+		$p->next_tag( array( 'tag_closers' => 'visit' ) );
+		$result = $p->append_content_after_template_tag_closer( $content_2 );
+		$this->assertTrue( $result );
+		$this->assertEquals( $content_1 . $content_2, $p );
+		$p->next_tag( array( 'tag_closers' => 'visit' ) );
+		$this->assertEquals( 'content-2', $p->get_attribute( 'class' ) );
+		// Rewinds to the first template.
+		$p->seek( 'first template' );
+		$p->release_bookmark( 'first template' );
+		$this->assertEquals( 'content-1', $p->get_attribute( 'class' ) );
+		$p->next_tag( array( 'tag_closers' => 'visit' ) );
+		$result = $p->append_content_after_template_tag_closer( $content_3 );
+		$this->assertEquals( $content_1 . $content_3 . $content_2, $p );
+		$p->next_tag( array( 'tag_closers' => 'visit' ) );
+		$this->assertEquals( 'content-3', $p->get_attribute( 'class' ) );
+	}
+
+	/**
+	 * Tests the `append_content_after_template_tag_closer` method on
+	 * set_attribute calls.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::append_content_after_template_tag_closer
+	 */
+	public function test_append_content_after_template_tag_closer_with_set_attribute() {
+		$content_1 = '<template>Text</template>';
+		$content_2 = '<template>New text</template>';
+
+		$p = new WP_Interactivity_API_Directives_Processor( $content_1 );
+		$p->next_tag( array( 'tag_closers' => 'visit' ) );
+		$p->set_attribute( 'class', 'test' );
+		$p->next_tag( array( 'tag_closers' => 'visit' ) );
+		$result = $p->append_content_after_template_tag_closer( $content_2 );
+		$this->assertTrue( $result );
+		$this->assertEquals( '<template class="test">Text</template>' . $content_2, $p );
+	}
+
+	/**
+	 * Tests the `append_content_after_template_tag_closer` method where the
+	 * existing content includes tags.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::append_content_after_template_tag_closer
+	 */
+	public function test_append_content_after_template_tag_closer_with_existing_tags() {
+		$content_1 = '<template><span>Text</span></template>';
+		$content_2 = '<template class="content-2-template-1"><template class="content-2-template-2">New text</template></template>';
+		$content_3 = '<template><span>More new text</span></template>';
+		$p         = new WP_Interactivity_API_Directives_Processor( $content_1 );
+		$p->next_tag();
+		$p->next_tag(
+			array(
+				'tag_name'    => 'template',
+				'tag_closers' => 'visit',
+			)
+		);
+		$result = $p->append_content_after_template_tag_closer( $content_2 );
+		$this->assertTrue( $result );
+		$this->assertEquals( $content_1 . $content_2, $p );
+		$p->next_tag();
+		$this->assertEquals( 'content-2-template-1', $p->get_attribute( 'class' ) );
+		$p->next_tag();
+		$this->assertEquals( 'content-2-template-2', $p->get_attribute( 'class' ) );
+		$p->next_tag( array( 'tag_closers' => 'visit' ) );
+		$result = $p->append_content_after_template_tag_closer( $content_3 );
+		$this->assertTrue( $result );
+		$this->assertEquals( $content_1 . '<template class="content-2-template-1"><template class="content-2-template-2">New text</template>' . $content_3 . '</template>', $p );
+	}
+
+	/**
+	 * Tests the `append_content_after_template_tag_closer` method fails with an
+	 * empty string.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::append_content_after_template_tag_closer
+	 */
+	public function test_append_content_after_template_tag_closer_empty() {
+		$content = '<template class="content">Text</template>';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag( array( 'tag_closers' => 'visit' ) );
+		$p->next_tag( array( 'tag_closers' => 'visit' ) );
+		$result = $p->append_content_after_template_tag_closer( '' );
+		$this->assertFalse( $result );
+		$this->assertEquals( $content, $p );
+		$this->assertEquals( 'TEMPLATE', $p->get_tag() ); // It didn't move.
+		$this->assertTrue( $p->is_tag_closer() ); // It didn't move.
+	}
+
+	/**
+	 * Tests the `append_content_after_template_tag_closer` method on a
+	 * non-existent tag.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::append_content_after_template_tag_closer
+	 */
+	public function test_append_content_after_template_tag_closer_non_existent_tag() {
+		$content_1 = 'Just a string with no tags.';
+		$content_2 = '<div>New text</div>';
+		$p         = new WP_Interactivity_API_Directives_Processor( $content_1 );
+		$p->next_tag();
+		$result = $p->append_content_after_template_tag_closer( $content_2 );
+		$this->assertFalse( $result );
+		$this->assertEquals( $content_1, $p );
+	}
+
+	/**
+	 * Tests the `append_content_after_template_tag_closer` method on non-template
+	 * tags.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::append_content_after_template_tag_closer
+	 */
+	public function test_append_content_after_template_tag_closer_non_template_tags() {
+		$content_1 = '<div>Text</div>';
+		$content_2 = '<div>New text</div>';
+		$p         = new WP_Interactivity_API_Directives_Processor( $content_1 );
+		$p->next_tag( array( 'tag_closers' => 'visit' ) );
+		$p->next_tag( array( 'tag_closers' => 'visit' ) );
+		$result = $p->append_content_after_template_tag_closer( $content_2 );
+		$this->assertFalse( $result );
+		$this->assertEquals( $content_1, $p );
+	}
+
+	/**
+	 * Tests that the `next_balanced_tag_closer_tag` method finds a closing tag
+	 * for a standard tag.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::next_balanced_tag_closer_tag
+	 */
+	public function test_next_balanced_tag_closer_tag_standard_tags() {
+		$content = '<div>Text</div>';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$this->assertTrue( $p->next_balanced_tag_closer_tag() );
+		$this->assertEquals( 'DIV', $p->get_tag() );
+		$this->assertTrue( $p->is_tag_closer() );
+	}
+
+	/**
+	 * Tests that the `next_balanced_tag_closer_tag` method returns false for a
+	 * self-closing tag.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::next_balanced_tag_closer_tag
+	 */
+	public function test_next_balanced_tag_closer_tag_void_tag() {
+		$content = '<img src="image.jpg" />';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$this->assertFalse( $p->next_balanced_tag_closer_tag() );
+
+		$content = '<img src="image.jpg" /><div>Text</div>';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$this->assertFalse( $p->next_balanced_tag_closer_tag() );
+	}
+
+	/**
+	 * Tests that the `next_balanced_tag_closer_tag` method correctly handles
+	 * nested tags.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::next_balanced_tag_closer_tag
+	 */
+	public function test_next_balanced_tag_closer_tag_nested_tags() {
+		$content = '<div><span>Nested content</span></div>';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$this->assertTrue( $p->next_balanced_tag_closer_tag() );
+		$this->assertEquals( 'DIV', $p->get_tag() );
+		$this->assertTrue( $p->is_tag_closer() );
+
+		$content = '<div><div>Nested content</div></div>';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$this->assertTrue( $p->next_balanced_tag_closer_tag() );
+		$this->assertEquals( 'DIV', $p->get_tag() );
+		$this->assertTrue( $p->is_tag_closer() );
+		$this->assertFalse( $p->next_tag() ); // No more content.
+	}
+
+	/**
+	 * Tests that the `next_balanced_tag_closer_tag` method returns false when no
+	 * matching closing tag is found.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::next_balanced_tag_closer_tag
+	 */
+	public function test_next_balanced_tag_closer_tag_no_matching_closing_tag() {
+		$content = '<div>No closing tag here';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+
+		$content = '<div><div>No closing tag here</div>';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		$p->next_tag();
+		$this->assertFalse( $p->next_balanced_tag_closer_tag() );
+	}
+
+	/**
+	 * Test that the `next_balanced_tag_closer_tag` method returns false when
+	 * returned on a closing tag.
+	 *
+	 * @ticket 60356
+	 *
+	 * @covers ::next_balanced_tag_closer_tag
+	 */
+	public function test_next_balanced_tag_closer_tag_on_closing_tag() {
+		$content = '<div>Closing tag after this</div>';
+		$p       = new WP_Interactivity_API_Directives_Processor( $content );
+		// Visit opening tag first and then closing tag.
+		$p->next_tag();
+		$p->next_tag( array( 'tag_closers' => 'visit' ) );
+		$this->assertFalse( $p->next_balanced_tag_closer_tag() );
+	}
+}