Add tests to check that invalid markup in CSS is rejected

tests/phpunit/tests/rest-api/rest-global-styles-controller.php

@@ -513,4 +513,38 @@ public function test_get_theme_items() {
 		);
 		$this->assertSameSetsWithIndex( $data, $expected );
 	}
+
+	/**
+	 * @covers WP_REST_Global_Styles_Controller::update_item
+	 * @ticket 57536
+	 */
+	public function test_update_item_valid_styles_css() {
+		wp_set_current_user( self::$admin_id );
+		$request = new WP_REST_Request( 'PUT', '/wp/v2/global-styles/' . self::$global_styles_id );
+		$request->set_body_params(
+			array(
+				'styles' => array( 'css' => 'body { color: red; }' ),
+			)
+		);
+		$response = rest_get_server()->dispatch( $request );
+		$data     = $response->get_data();
+		$this->assertSame( 'body { color: red; }', $data['styles']['css'] );
+	}
+
+	/**
+	 * @covers WP_REST_Global_Styles_Controller::update_item
+	 * @ticket 57536
+	 */
+	public function test_update_item_invalid_styles_css() {
+		wp_set_current_user( self::$admin_id );
+		$request = new WP_REST_Request( 'PUT', '/wp/v2/global-styles/' . self::$global_styles_id );
+		$request->set_body_params(
+			array(
+				'styles' => array( 'css' => '<p>test</p> body { color: red; }' ),
+			)
+		);
+		$response = rest_get_server()->dispatch( $request );
+		$this->assertErrorResponse( 'rest_custom_css_illegal_markup', $response, 400 );
+	}
+
 }