diff --git a/spring-test/src/main/java/org/springframework/test/web/client/match/MockRestRequestMatchers.java b/spring-test/src/main/java/org/springframework/test/web/client/match/MockRestRequestMatchers.java
index d4c164dddd54..a61189199251 100644
--- a/spring-test/src/main/java/org/springframework/test/web/client/match/MockRestRequestMatchers.java
+++ b/spring-test/src/main/java/org/springframework/test/web/client/match/MockRestRequestMatchers.java
@@ -23,7 +23,6 @@
 import javax.xml.xpath.XPathExpressionException;
 
 import org.hamcrest.Matcher;
-import org.hamcrest.Matchers;
 
 import org.springframework.http.HttpMethod;
 import org.springframework.http.client.ClientHttpRequest;
@@ -48,6 +47,7 @@
  * @author Craig Walls
  * @author Rossen Stoyanchev
  * @author Sam Brannen
+ * @author Simon Baslé
  * @since 3.2
  */
 public abstract class MockRestRequestMatchers {
@@ -113,13 +113,49 @@ public static RequestMatcher requestTo(URI uri) {
 		return request -> assertEquals("Unexpected request", uri, request.getURI());
 	}
 
+	/**
+	 * Assert request query parameter values with the given Hamcrest matcher,
+	 * matching on the entire {@link List} of values.
+	 * <p>For example, this can be used to check that the list of query parameter
+	 * values has at least one value matching a given Hamcrest matcher (such as
+	 * {@link org.hamcrest.Matchers#hasItem(Matcher)}), that every value in the list
+	 * matches common criteria (such as {@link org.hamcrest.Matchers#everyItem(Matcher)}),
+	 * that each value in the list matches corresponding dedicated criteria
+	 * (such as {@link org.hamcrest.Matchers#contains(Matcher[])}, etc.
+	 * @param name the name of the query parameter whose value(s) will be asserted
+	 * @param matcher the Hamcrest matcher to apply to the entire list of values
+	 * for the given query parameter
+	 * @since 5.3.26
+	 * @see #queryParam(String, Matcher...)
+	 * @see #queryParam(String, String...)
+	 */
+	public static RequestMatcher queryParam(String name, Matcher<? super List<String>> matcher) {
+		return request -> {
+			MultiValueMap<String, String> params = getQueryParams(request);
+			List<String> paramValues = params.get(name);
+			if (paramValues == null) {
+				fail("Expected query param <" + name + "> to exist but was null");
+			}
+			assertThat("Query param [" + name + "] values", paramValues, matcher);
+		};
+	}
+
 	/**
 	 * Assert request query parameter values with the given Hamcrest matcher(s).
-	 * <p>Note that if the queryParam value list is larger than the number of provided
-	 * {@code matchers}, extra values are considered acceptable.
-	 * See {@link #queryParam(String, Matcher)} for a variant that takes a
-	 * {@code Matcher} over the whole list of values.
+	 * <p>If the query parameter value list is larger than the number of provided
+	 * {@code matchers}, no matchers will be applied to the extra query parameter
+	 * values, effectively ignoring the additional parameter values. If the number
+	 * of provided {@code matchers} exceeds the number of query parameter values,
+	 * an {@link AssertionError} will be thrown to signal the mismatch.
+	 * <p>See {@link #queryParam(String, Matcher)} for a variant which accepts a
+	 * {@code Matcher} that applies to the entire list of values as opposed to
+	 * applying only to individual values.
+	 * @param name the name of the query parameter whose value(s) will be asserted
+	 * @param matchers the Hamcrest matchers to apply to individual query parameter
+	 * values; the n<sup>th</sup> matcher is applied to the n<sup>th</sup> query
+	 * parameter value
 	 * @see #queryParam(String, Matcher)
+	 * @see #queryParam(String, String...)
 	 */
 	@SafeVarargs
 	public static RequestMatcher queryParam(String name, Matcher<? super String>... matchers) {
@@ -134,11 +170,20 @@ public static RequestMatcher queryParam(String name, Matcher<? super String>...
 
 	/**
 	 * Assert request query parameter values.
-	 * <p>Note that if the queryParam value list is larger than {@code expectedValues},
-	 * extra values are considered acceptable.
-	 * See {@link #queryParam(String, Matcher)} for a variant that takes a
-	 * {@code Matcher} over the whole list of values.
+	 * <p>If the query parameter value list is larger than the number of
+	 * {@code expectedValues}, no assertions will be applied to the extra query
+	 * parameter values, effectively ignoring the additional parameter values. If
+	 * the number of {@code expectedValues} exceeds the number of query parameter
+	 * values, an {@link AssertionError} will be thrown to signal the mismatch.
+	 * <p>See {@link #queryParam(String, Matcher)} for a variant which accepts a
+	 * Hamcrest {@code Matcher} that applies to the entire list of values as opposed
+	 * to asserting only individual values.
+	 * @param name the name of the query parameter whose value(s) will be asserted
+	 * @param expectedValues the expected values of individual query parameter values;
+	 * the n<sup>th</sup> expected value is compared to the n<sup>th</sup> query
+	 * parameter value
 	 * @see #queryParam(String, Matcher)
+	 * @see #queryParam(String, Matcher...)
 	 */
 	public static RequestMatcher queryParam(String name, String... expectedValues) {
 		return request -> {
@@ -150,53 +195,51 @@ public static RequestMatcher queryParam(String name, String... expectedValues) {
 		};
 	}
 
+	private static MultiValueMap<String, String> getQueryParams(ClientHttpRequest request) {
+		return UriComponentsBuilder.fromUri(request.getURI()).build().getQueryParams();
+	}
+
 	/**
-	 * Assert request query parameter, matching on the whole {@code List} of values.
-	 * <p>This can be used to check that the list has at least one value matching a
-	 * criteria ({@link Matchers#hasItem(Matcher)}), or that every value in the list
-	 * matches a common criteria ({@link Matchers#everyItem(Matcher)}), or that each
-	 * value in the list matches its corresponding dedicated criteria
-	 * ({@link Matchers#contains(Matcher[])}, and more.
-	 * @param name the name of the query parameter to consider
-	 * @param matcher the matcher to apply to the whole list of values for that header
+	 * Assert request header values with the given Hamcrest matcher, matching on
+	 * the entire {@link List} of values.
+	 * <p>For example, this can be used to check that the list of header values
+	 * has at least one value matching a given Hamcrest matcher (such as
+	 * {@link org.hamcrest.Matchers#hasItem(Matcher)}), that every value in the list
+	 * matches common criteria (such as {@link org.hamcrest.Matchers#everyItem(Matcher)}),
+	 * that each value in the list matches corresponding dedicated criteria
+	 * (such as {@link org.hamcrest.Matchers#contains(Matcher[])}, etc.
+	 * @param name the name of the header whose value(s) will be asserted
+	 * @param matcher the Hamcrest matcher to apply to the entire list of values
+	 * for the given header
 	 * @since 5.3.26
+	 * @see #header(String, Matcher...)
+	 * @see #header(String, String...)
 	 */
-	public static RequestMatcher queryParam(String name, Matcher<? super List<String>> matcher) {
+	public static RequestMatcher header(String name, Matcher<? super List<String>> matcher) {
 		return request -> {
-			MultiValueMap<String, String> params = getQueryParams(request);
-			List<String> paramValues = params.get(name);
-			if (paramValues == null) {
-				fail("No queryParam [" + name + "]");
+			List<String> headerValues = request.getHeaders().get(name);
+			if (headerValues == null) {
+				fail("Expected header <" + name + "> to exist but was null");
 			}
-			assertThat("Request queryParam values for [" + name + "]", paramValues, matcher);
+			assertThat("Request header [" + name + "] values", headerValues, matcher);
 		};
 	}
 
-
-	private static MultiValueMap<String, String> getQueryParams(ClientHttpRequest request) {
-		return UriComponentsBuilder.fromUri(request.getURI()).build().getQueryParams();
-	}
-
-	private static void assertValueCount(
-			String valueType, String name, MultiValueMap<String, String> map, int count) {
-
-		List<String> values = map.get(name);
-		String message = "Expected " + valueType + " <" + name + ">";
-		if (values == null) {
-			fail(message + " to exist but was null");
-		}
-		if (count > values.size()) {
-			fail(message + " to have at least <" + count + "> values but found " + values);
-		}
-	}
-
 	/**
 	 * Assert request header values with the given Hamcrest matcher(s).
-	 * <p>Note that if the header's value list is larger than the number of provided
-	 * {@code matchers}, extra values are considered acceptable.
-	 * See {@link #header(String, Matcher)} for a variant that takes a {@code Matcher}
-	 * over the whole list of values.
+	 * <p>If the header value list is larger than the number of provided
+	 * {@code matchers}, no matchers will be applied to the extra header values,
+	 * effectively ignoring the additional header values. If the number of
+	 * provided {@code matchers} exceeds the number of header values, an
+	 * {@link AssertionError} will be thrown to signal the mismatch.
+	 * <p>See {@link #header(String, Matcher)} for a variant which accepts a
+	 * Hamcrest {@code Matcher} that applies to the entire list of values as
+	 * opposed to applying only to individual values.
+	 * @param name the name of the header whose value(s) will be asserted
+	 * @param matchers the Hamcrest matchers to apply to individual header values;
+	 * the n<sup>th</sup> matcher is applied to the n<sup>th</sup> header value
 	 * @see #header(String, Matcher)
+	 * @see #header(String, String...)
 	 */
 	@SafeVarargs
 	public static RequestMatcher header(String name, Matcher<? super String>... matchers) {
@@ -212,11 +255,19 @@ public static RequestMatcher header(String name, Matcher<? super String>... matc
 
 	/**
 	 * Assert request header values.
-	 * <p>Note that if the header's value list is larger than {@code expectedValues},
-	 * extra values are considered acceptable.
-	 * See {@link #header(String, Matcher)} for a variant that takes a {@code Matcher}
-	 * over the whole list of values.
+	 * <p>If the header value list is larger than the number of {@code expectedValues},
+	 * no matchers will be applied to the extra header values, effectively ignoring the
+	 * additional header values. If the number of {@code expectedValues} exceeds the
+	 * number of header values, an {@link AssertionError} will be thrown to signal the
+	 * mismatch.
+	 * <p>See {@link #header(String, Matcher)} for a variant which accepts a
+	 * Hamcrest {@code Matcher} that applies to the entire list of values as
+	 * opposed to applying only to individual values.
+	 * @param name the name of the header whose value(s) will be asserted
+	 * @param expectedValues the expected values of individual header values; the
+	 * n<sup>th</sup> expected value is compared to the n<sup>th</sup> header value
 	 * @see #header(String, Matcher)
+	 * @see #header(String, Matcher...)
 	 */
 	public static RequestMatcher header(String name, String... expectedValues) {
 		return request -> {
@@ -229,27 +280,6 @@ public static RequestMatcher header(String name, String... expectedValues) {
 		};
 	}
 
-	/**
-	 * Assert request header, matching on the whole {@code List} of values.
-	 * <p>This can be used to check that the list has at least one value matching a
-	 * criteria ({@link Matchers#hasItem(Matcher)}), or that every value in the list
-	 * matches a common criteria ({@link Matchers#everyItem(Matcher)}), or that each
-	 * value in the list matches its corresponding dedicated criteria
-	 * ({@link Matchers#contains(Matcher[])}, and more.
-	 * @param name the name of the request header to consider
-	 * @param matcher the matcher to apply to the whole list of values for that header
-	 * @since 5.3.26
-	 */
-	public static RequestMatcher header(String name, Matcher<? super List<String>> matcher) {
-		return request -> {
-			List<String> headerValues = request.getHeaders().get(name);
-			if (headerValues == null) {
-				fail("No header values for header [" + name + "]");
-			}
-			assertThat("Request header values for [" + name + "]", headerValues, matcher);
-		};
-	}
-
 	/**
 	 * Assert that the given request header does not exist.
 	 * @since 5.2
@@ -323,4 +353,18 @@ public static XpathRequestMatchers xpath(String expression, Map<String, String>
 		return new XpathRequestMatchers(expression, namespaces, args);
 	}
 
+
+	private static void assertValueCount(
+			String valueType, String name, MultiValueMap<String, String> map, int count) {
+
+		List<String> values = map.get(name);
+		String message = "Expected " + valueType + " <" + name + ">";
+		if (values == null) {
+			fail(message + " to exist but was null");
+		}
+		if (count > values.size()) {
+			fail(message + " to have at least <" + count + "> values but found " + values);
+		}
+	}
+
 }
diff --git a/spring-test/src/test/java/org/springframework/test/web/client/match/MockRestRequestMatchersTests.java b/spring-test/src/test/java/org/springframework/test/web/client/match/MockRestRequestMatchersTests.java
index a6e156514920..6b575533c18f 100644
--- a/spring-test/src/test/java/org/springframework/test/web/client/match/MockRestRequestMatchersTests.java
+++ b/spring-test/src/test/java/org/springframework/test/web/client/match/MockRestRequestMatchersTests.java
@@ -18,25 +18,23 @@
 
 import java.io.IOException;
 import java.net.URI;
-import java.util.Arrays;
-import java.util.Collections;
 import java.util.List;
 
-import org.hamcrest.CoreMatchers;
+import org.assertj.core.api.AssertionsForClassTypes;
+import org.assertj.core.api.ThrowableTypeAssert;
 import org.hamcrest.Matchers;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.http.HttpMethod;
 import org.springframework.mock.http.client.MockClientHttpRequest;
 
-import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
-import static org.assertj.core.api.Assertions.assertThatThrownBy;
 import static org.hamcrest.Matchers.allOf;
 import static org.hamcrest.Matchers.any;
 import static org.hamcrest.Matchers.anything;
 import static org.hamcrest.Matchers.contains;
 import static org.hamcrest.Matchers.containsInAnyOrder;
 import static org.hamcrest.Matchers.containsString;
+import static org.hamcrest.Matchers.either;
 import static org.hamcrest.Matchers.endsWith;
 import static org.hamcrest.Matchers.everyItem;
 import static org.hamcrest.Matchers.hasItem;
@@ -52,6 +50,7 @@
  * @author Craig Walls
  * @author Rossen Stoyanchev
  * @author Sam Brannen
+ * @author Simon Baslé
  */
 class MockRestRequestMatchersTests {
 
@@ -76,9 +75,8 @@ void requestToUriTemplate() throws Exception {
 	void requestToNoMatch() {
 		this.request.setURI(URI.create("http://www.foo.example/bar"));
 
-		assertThatThrownBy(
-			() -> MockRestRequestMatchers.requestTo("http://www.foo.example/wrong").match(this.request))
-				.isInstanceOf(AssertionError.class);
+		assertThatAssertionError()
+			.isThrownBy(() -> MockRestRequestMatchers.requestTo("http://www.foo.example/wrong").match(this.request));
 	}
 
 	@Test
@@ -99,14 +97,14 @@ void method() throws Exception {
 	void methodNoMatch() {
 		this.request.setMethod(HttpMethod.POST);
 
-		assertThatThrownBy(() -> MockRestRequestMatchers.method(HttpMethod.GET).match(this.request))
-			.isInstanceOf(AssertionError.class)
-			.hasMessageContaining("expected:<GET> but was:<POST>");
+		assertThatAssertionError()
+			.isThrownBy(() -> MockRestRequestMatchers.method(HttpMethod.GET).match(this.request))
+			.withMessageContaining("expected:<GET> but was:<POST>");
 	}
 
 	@Test
 	void header() throws Exception {
-		this.request.getHeaders().put("foo", Arrays.asList("bar", "baz"));
+		this.request.getHeaders().put("foo", List.of("bar", "baz"));
 
 		MockRestRequestMatchers.header("foo", "bar", "baz").match(this.request);
 	}
@@ -117,62 +115,62 @@ void headerDoesNotExist() throws Exception {
 		MockRestRequestMatchers.headerDoesNotExist("").match(this.request);
 		MockRestRequestMatchers.headerDoesNotExist("foo").match(this.request);
 
-		List<String> values = Arrays.asList("bar", "baz");
+		List<String> values = List.of("bar", "baz");
 		this.request.getHeaders().put("foo", values);
-		assertThatThrownBy(() -> MockRestRequestMatchers.headerDoesNotExist("foo").match(this.request))
-			.isInstanceOf(AssertionError.class)
-			.hasMessage("Expected header <foo> not to exist, but it exists with values: " + values);
+		assertThatAssertionError()
+			.isThrownBy(() -> MockRestRequestMatchers.headerDoesNotExist("foo").match(this.request))
+			.withMessage("Expected header <foo> not to exist, but it exists with values: " + values);
 	}
 
 	@Test
 	void headerMissing() {
-		assertThatThrownBy(() -> MockRestRequestMatchers.header("foo", "bar").match(this.request))
-			.isInstanceOf(AssertionError.class)
-			.hasMessageContaining("was null");
+		assertThatAssertionError()
+			.isThrownBy(() -> MockRestRequestMatchers.header("foo", "bar").match(this.request))
+			.withMessageContaining("was null");
 	}
 
 	@Test
 	void headerMissingValue() {
-		this.request.getHeaders().put("foo", Arrays.asList("bar", "baz"));
+		this.request.getHeaders().put("foo", List.of("bar", "baz"));
 
-		assertThatThrownBy(() -> MockRestRequestMatchers.header("foo", "bad").match(this.request))
-			.isInstanceOf(AssertionError.class)
-			.hasMessageContaining("expected:<bad> but was:<bar>");
+		assertThatAssertionError()
+			.isThrownBy(() -> MockRestRequestMatchers.header("foo", "bad").match(this.request))
+			.withMessageContaining("expected:<bad> but was:<bar>");
 	}
 
 	@Test
 	void headerContains() throws Exception {
-		this.request.getHeaders().put("foo", Arrays.asList("bar", "baz"));
+		this.request.getHeaders().put("foo", List.of("bar", "baz"));
 
 		MockRestRequestMatchers.header("foo", containsString("ba")).match(this.request);
 	}
 
 	@Test
 	void headerContainsWithMissingHeader() {
-		assertThatThrownBy(() -> MockRestRequestMatchers.header("foo", containsString("baz")).match(this.request))
-			.isInstanceOf(AssertionError.class)
-			.hasMessageContaining("but was null");
+		assertThatAssertionError()
+			.isThrownBy(() -> MockRestRequestMatchers.header("foo", containsString("baz")).match(this.request))
+			.withMessageContaining("but was null");
 	}
 
 	@Test
 	void headerContainsWithMissingValue() {
-		this.request.getHeaders().put("foo", Arrays.asList("bar", "baz"));
+		this.request.getHeaders().put("foo", List.of("bar", "baz"));
 
-		assertThatThrownBy(() -> MockRestRequestMatchers.header("foo", containsString("bx")).match(this.request))
-			.isInstanceOf(AssertionError.class)
-			.hasMessageContaining("was \"bar\"");
+		assertThatAssertionError()
+			.isThrownBy(() -> MockRestRequestMatchers.header("foo", containsString("bx")).match(this.request))
+			.withMessageContaining("was \"bar\"");
 	}
 
 	@Test
 	void headerListMissing() {
-		assertThatThrownBy(() -> MockRestRequestMatchers.header("foo", hasSize(2)).match(this.request))
-				.isInstanceOf(AssertionError.class)
-				.hasMessage("No header values for header [foo]");
+		assertThatAssertionError()
+			.isThrownBy(() -> MockRestRequestMatchers.header("foo", hasSize(2)).match(this.request))
+			.withMessage("Expected header <foo> to exist but was null");
 	}
 
 	@Test
 	void headerListMatchers() throws IOException {
-		this.request.getHeaders().put("foo", Arrays.asList("bar", "baz"));
+		this.request.getHeaders().put("foo", List.of("bar", "baz"));
 
 		MockRestRequestMatchers.header("foo", containsInAnyOrder(endsWith("baz"), endsWith("bar"))).match(this.request);
 		MockRestRequestMatchers.header("foo", contains(is("bar"), is("baz"))).match(this.request);
@@ -181,66 +179,71 @@ void headerListMatchers() throws IOException {
 		MockRestRequestMatchers.header("foo", everyItem(startsWith("ba"))).match(this.request);
 		MockRestRequestMatchers.header("foo", hasSize(2)).match(this.request);
 
-		//these can be a bit ambiguous when reading the test (the compiler selects the list matcher):
+		// These can be a bit ambiguous when reading the test (the compiler selects the list matcher):
 		MockRestRequestMatchers.header("foo", notNullValue()).match(this.request);
 		MockRestRequestMatchers.header("foo", is(anything())).match(this.request);
 		MockRestRequestMatchers.header("foo", allOf(notNullValue(), notNullValue())).match(this.request);
 
-		//these are not as ambiguous thanks to an inner matcher that is either obviously list-oriented,
-		//string-oriented or obviously a vararg of matchers
-		//list matcher version
+		// These are not as ambiguous thanks to an inner matcher that is either obviously list-oriented,
+		// string-oriented, or obviously a vararg of matchers
+
+		// list matcher version
 		MockRestRequestMatchers.header("foo", allOf(notNullValue(), hasSize(2))).match(this.request);
-		//vararg version
+
+		// vararg version
 		MockRestRequestMatchers.header("foo", allOf(notNullValue(), endsWith("ar"))).match(this.request);
 		MockRestRequestMatchers.header("foo", is((any(String.class)))).match(this.request);
-		MockRestRequestMatchers.header("foo", CoreMatchers.either(is("bar")).or(is(nullValue()))).match(this.request);
+		MockRestRequestMatchers.header("foo", either(is("bar")).or(is(nullValue()))).match(this.request);
 		MockRestRequestMatchers.header("foo", is(notNullValue()), is(notNullValue())).match(this.request);
 	}
 
 	@Test
 	void headerListContainsMismatch() {
-		this.request.getHeaders().put("foo", Arrays.asList("bar", "baz"));
-
-		assertThatExceptionOfType(AssertionError.class).isThrownBy(() -> MockRestRequestMatchers
-						.header("foo", contains(containsString("ba"))).match(this.request))
-				.withMessage("Request header values for [foo]" + System.lineSeparator()
-						+ "Expected: iterable containing [a string containing \"ba\"]" + System.lineSeparator()
-						+ "     but: not matched: \"baz\"");
-
-		assertThatExceptionOfType(AssertionError.class).isThrownBy(() -> MockRestRequestMatchers
-						.header("foo", hasItem(endsWith("ba"))).match(this.request))
-				.withMessage("Request header values for [foo]" + System.lineSeparator()
-						+ "Expected: a collection containing a string ending with \"ba\"" + System.lineSeparator()
-						+ "     but: mismatches were: [was \"bar\", was \"baz\"]");
-
-		assertThatExceptionOfType(AssertionError.class).isThrownBy(() -> MockRestRequestMatchers
-						.header("foo", everyItem(endsWith("ar"))).match(this.request))
-				.withMessage("Request header values for [foo]" + System.lineSeparator()
-						+ "Expected: every item is a string ending with \"ar\"" + System.lineSeparator()
-						+ "     but: an item was \"baz\"");
+		this.request.getHeaders().put("foo", List.of("bar", "baz"));
+
+		assertThatAssertionError()
+			.isThrownBy(() -> MockRestRequestMatchers.header("foo", contains(containsString("ba"))).match(this.request))
+			.withMessageContainingAll(
+					"Request header [foo] values",
+					"Expected: iterable containing [a string containing \"ba\"]",
+					"but: not matched: \"baz\"");
+
+		assertThatAssertionError()
+			.isThrownBy(() -> MockRestRequestMatchers.header("foo", hasItem(endsWith("ba"))).match(this.request))
+			.withMessageContainingAll(
+					"Request header [foo] values",
+					"Expected: a collection containing a string ending with \"ba\"",
+					"but: mismatches were: [was \"bar\", was \"baz\"]");
+
+		assertThatAssertionError()
+			.isThrownBy(() -> MockRestRequestMatchers.header("foo", everyItem(endsWith("ar"))).match(this.request))
+			.withMessageContainingAll(
+					"Request header [foo] values",
+					"Expected: every item is a string ending with \"ar\"",
+					"but: an item was \"baz\"");
 	}
 
 	@Test
 	void headers() throws Exception {
-		this.request.getHeaders().put("foo", Arrays.asList("bar", "baz"));
+		this.request.getHeaders().put("foo", List.of("bar", "baz"));
 
 		MockRestRequestMatchers.header("foo", "bar", "baz").match(this.request);
 	}
 
 	@Test
 	void headersWithMissingHeader() {
-		assertThatThrownBy(() -> MockRestRequestMatchers.header("foo", "bar").match(this.request))
-			.isInstanceOf(AssertionError.class)
-			.hasMessageContaining("but was null");
+		assertThatAssertionError()
+			.isThrownBy(() -> MockRestRequestMatchers.header("foo", "bar").match(this.request))
+			.withMessageContaining("but was null");
 	}
 
 	@Test
 	void headersWithMissingValue() {
-		this.request.getHeaders().put("foo", Collections.singletonList("bar"));
+		this.request.getHeaders().put("foo", List.of("bar"));
 
-		assertThatThrownBy(() -> MockRestRequestMatchers.header("foo", "bar", "baz").match(this.request))
-			.isInstanceOf(AssertionError.class)
-			.hasMessageContaining("to have at least <2> values");
+		assertThatAssertionError()
+			.isThrownBy(() -> MockRestRequestMatchers.header("foo", "bar", "baz").match(this.request))
+			.withMessageContaining("to have at least <2> values");
 	}
 
 	@Test
@@ -254,18 +257,18 @@ void queryParam() throws Exception {
 	void queryParamMissing() {
 		this.request.setURI(URI.create("http://www.foo.example/a"));
 
-		assertThatThrownBy(() -> MockRestRequestMatchers.queryParam("foo", "bar").match(this.request))
-			.isInstanceOf(AssertionError.class)
-			.hasMessageContaining("but was null");
+		assertThatAssertionError()
+			.isThrownBy(() -> MockRestRequestMatchers.queryParam("foo", "bar").match(this.request))
+			.withMessageContaining("but was null");
 	}
 
 	@Test
 	void queryParamMissingValue() {
 		this.request.setURI(URI.create("http://www.foo.example/a?foo=bar&foo=baz"));
 
-		assertThatThrownBy(() -> MockRestRequestMatchers.queryParam("foo", "bad").match(this.request))
-			.isInstanceOf(AssertionError.class)
-			.hasMessageContaining("expected:<bad> but was:<bar>");
+		assertThatAssertionError()
+			.isThrownBy(() -> MockRestRequestMatchers.queryParam("foo", "bad").match(this.request))
+			.withMessageContaining("expected:<bad> but was:<bar>");
 	}
 
 	@Test
@@ -279,17 +282,17 @@ void queryParamContains() throws Exception {
 	void queryParamContainsWithMissingValue() {
 		this.request.setURI(URI.create("http://www.foo.example/a?foo=bar&foo=baz"));
 
-		assertThatThrownBy(() -> MockRestRequestMatchers.queryParam("foo", containsString("bx")).match(this.request))
-			.isInstanceOf(AssertionError.class)
-			.hasMessageContaining("was \"bar\"");
+		assertThatAssertionError()
+			.isThrownBy(() -> MockRestRequestMatchers.queryParam("foo", containsString("bx")).match(this.request))
+			.withMessageContaining("was \"bar\"");
 	}
 
 
 	@Test
 	void queryParamListMissing() {
-		assertThatThrownBy(() -> MockRestRequestMatchers.queryParam("foo", hasSize(2)).match(this.request))
-				.isInstanceOf(AssertionError.class)
-				.hasMessage("No queryParam [foo]");
+		assertThatAssertionError()
+			.isThrownBy(() -> MockRestRequestMatchers.queryParam("foo", hasSize(2)).match(this.request))
+			.withMessage("Expected query param <foo> to exist but was null");
 	}
 
 	@Test
@@ -303,19 +306,21 @@ void queryParamListMatchers() throws IOException {
 		MockRestRequestMatchers.queryParam("foo", everyItem(startsWith("ba"))).match(this.request);
 		MockRestRequestMatchers.queryParam("foo", hasSize(2)).match(this.request);
 
-		//these can be a bit ambiguous when reading the test (the compiler selects the list matcher):
+		// These can be a bit ambiguous when reading the test (the compiler selects the list matcher):
 		MockRestRequestMatchers.queryParam("foo", notNullValue()).match(this.request);
 		MockRestRequestMatchers.queryParam("foo", is(anything())).match(this.request);
 		MockRestRequestMatchers.queryParam("foo", allOf(notNullValue(), notNullValue())).match(this.request);
 
-		//these are not as ambiguous thanks to an inner matcher that is either obviously list-oriented,
-		//string-oriented or obviously a vararg of matchers
-		//list matcher version
+		// These are not as ambiguous thanks to an inner matcher that is either obviously list-oriented,
+		// string-oriented, or obviously a vararg of matchers
+
+		// list matcher version
 		MockRestRequestMatchers.queryParam("foo", allOf(notNullValue(), hasSize(2))).match(this.request);
-		//vararg version
+
+		// vararg version
 		MockRestRequestMatchers.queryParam("foo", allOf(notNullValue(), endsWith("ar"))).match(this.request);
 		MockRestRequestMatchers.queryParam("foo", is((any(String.class)))).match(this.request);
-		MockRestRequestMatchers.queryParam("foo", CoreMatchers.either(is("bar")).or(is(nullValue()))).match(this.request);
+		MockRestRequestMatchers.queryParam("foo", either(is("bar")).or(is(nullValue()))).match(this.request);
 		MockRestRequestMatchers.queryParam("foo", is(notNullValue()), is(notNullValue())).match(this.request);
 	}
 
@@ -323,23 +328,30 @@ void queryParamListMatchers() throws IOException {
 	void queryParamListContainsMismatch() {
 		this.request.setURI(URI.create("http://www.foo.example/a?foo=bar&foo=baz"));
 
-		assertThatExceptionOfType(AssertionError.class).isThrownBy(() -> MockRestRequestMatchers
-						.queryParam("foo", contains(containsString("ba"))).match(this.request))
-				.withMessage("Request queryParam values for [foo]" + System.lineSeparator()
-						+ "Expected: iterable containing [a string containing \"ba\"]" + System.lineSeparator()
-						+ "     but: not matched: \"baz\"");
-
-		assertThatExceptionOfType(AssertionError.class).isThrownBy(() -> MockRestRequestMatchers
-						.queryParam("foo", hasItem(endsWith("ba"))).match(this.request))
-				.withMessage("Request queryParam values for [foo]" + System.lineSeparator()
-						+ "Expected: a collection containing a string ending with \"ba\"" + System.lineSeparator()
-						+ "     but: mismatches were: [was \"bar\", was \"baz\"]");
-
-		assertThatExceptionOfType(AssertionError.class).isThrownBy(() -> MockRestRequestMatchers
-						.queryParam("foo", everyItem(endsWith("ar"))).match(this.request))
-				.withMessage("Request queryParam values for [foo]" + System.lineSeparator()
-						+ "Expected: every item is a string ending with \"ar\"" + System.lineSeparator()
-						+ "     but: an item was \"baz\"");
+		assertThatAssertionError()
+			.isThrownBy(() -> MockRestRequestMatchers.queryParam("foo", contains(containsString("ba"))).match(this.request))
+			.withMessageContainingAll(
+				"Query param [foo] values",
+				"Expected: iterable containing [a string containing \"ba\"]",
+				"but: not matched: \"baz\"");
+
+		assertThatAssertionError()
+			.isThrownBy(() -> MockRestRequestMatchers.queryParam("foo", hasItem(endsWith("ba"))).match(this.request))
+			.withMessageContainingAll(
+				"Query param [foo] values",
+				"Expected: a collection containing a string ending with \"ba\"",
+				"but: mismatches were: [was \"bar\", was \"baz\"]");
+
+		assertThatAssertionError()
+			.isThrownBy(() -> MockRestRequestMatchers.queryParam("foo", everyItem(endsWith("ar"))).match(this.request))
+			.withMessageContainingAll(
+				"Query param [foo] values",
+				"Expected: every item is a string ending with \"ar\"",
+				"but: an item was \"baz\"");
+	}
+
+	private static ThrowableTypeAssert<AssertionError> assertThatAssertionError() {
+		return AssertionsForClassTypes.assertThatExceptionOfType(AssertionError.class);
 	}
 
 }