Migrate JUnit Jupiter assertions to AssertJ

Migrate all existing JUnit Jupiter based assertions to AssertJ and add
Checkstyle rules to ensure they don't return.

See gh-23022

spring-test/src/test/java/org/springframework/test/context/junit/jupiter/ComposedSpringExtensionTests.java

@@ -28,8 +28,7 @@ import org.springframework.test.context.ContextConfiguration;
 import org.springframework.test.context.junit.SpringJUnitJupiterTestSuite;
 import org.springframework.test.context.junit.jupiter.comics.Person;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.assertj.core.api.Assertions.assertThat;
 
 /**
  * Integration tests which demonstrate the composability of annotations from
@@ -61,16 +60,16 @@ class ComposedSpringExtensionTests {
 	@Test
 	@DisplayName("ApplicationContext injected into method")
 	void applicationContextInjected(ApplicationContext applicationContext) {
-		assertNotNull(applicationContext, "ApplicationContext should have been injected into method by Spring");
-		assertEquals(dilbert, applicationContext.getBean("dilbert", Person.class));
+		assertThat(applicationContext).as("ApplicationContext should have been injected into method by Spring").isNotNull();
+		assertThat(applicationContext.getBean("dilbert", Person.class)).isEqualTo(dilbert);
 	}
 
 	@Test
 	@DisplayName("Spring @Beans injected into fields")
 	void springBeansInjected() {
-		assertNotNull(dilbert, "Person should have been @Autowired by Spring");
-		assertEquals("Dilbert", dilbert.getName(), "Person's name");
-		assertEquals(2, people.size(), "Number of Person objects in context");
+		assertThat(dilbert).as("Person should have been @Autowired by Spring").isNotNull();
+		assertThat(dilbert.getName()).as("Person's name").isEqualTo("Dilbert");
+		assertThat(people).as("Number of Person objects in context").hasSize(2);
 	}
 
 }

spring-test/src/test/java/org/springframework/test/context/junit/jupiter/DisabledIfConditionTests.java

@@ -30,11 +30,10 @@ import org.springframework.test.context.junit.SpringJUnitJupiterTestSuite;
 import org.springframework.util.ReflectionUtils;
 
 import static org.assertj.core.api.Assertions.assertThat;
-import static org.junit.jupiter.api.Assertions.assertAll;
-import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.assertj.core.api.Assertions.assertThatIllegalStateException;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.BDDMockito.given;
-import static org.mockito.Mockito.mock;
+import static org.mockito.BDDMockito.mock;
 
 /**
  * Tests for {@link DisabledIfCondition} that verify actual condition evaluation
@@ -62,34 +61,30 @@ class DisabledIfConditionTests {
 
 	@Test
 	void disabledByEmptyExpression() {
-		// @formatter:off
-		assertAll(
-			() -> assertExpressionIsBlank("emptyExpression"),
-			() -> assertExpressionIsBlank("blankExpression")
-		);
-		// @formatter:on
+		assertExpressionIsBlank("emptyExpression");
+		assertExpressionIsBlank("blankExpression");
 	}
 
 	@Test
 	void invalidExpressionEvaluationType() {
 		String methodName = "nonBooleanOrStringExpression";
-		IllegalStateException exception = assertThrows(IllegalStateException.class,
-			() -> condition.evaluateExecutionCondition(buildExtensionContext(methodName)));
-
 		Method method = ReflectionUtils.findMethod(getClass(), methodName);
 
-		assertThat(exception).hasMessage("@DisabledIf(\"#{6 * 7}\") on " + method + " must evaluate to a String or a Boolean, not java.lang.Integer");
+		assertThatIllegalStateException()
+			.isThrownBy(() -> condition.evaluateExecutionCondition(buildExtensionContext(methodName)))
+			.withMessageContaining(
+				"@DisabledIf(\"#{6 * 7}\") on " + method + " must evaluate to a String or a Boolean, not java.lang.Integer");
 	}
 
 	@Test
 	void unsupportedStringEvaluationValue() {
 		String methodName = "stringExpressionThatIsNeitherTrueNorFalse";
-		IllegalStateException exception = assertThrows(IllegalStateException.class,
-			() -> condition.evaluateExecutionCondition(buildExtensionContext(methodName)));
-
 		Method method = ReflectionUtils.findMethod(getClass(), methodName);
 
-		assertThat(exception).hasMessage("@DisabledIf(\"#{'enigma'}\") on " + method + " must evaluate to \"true\" or \"false\", not \"enigma\"");
+		assertThatIllegalStateException()
+			.isThrownBy(() -> condition.evaluateExecutionCondition(buildExtensionContext(methodName)))
+			.withMessageContaining(
+				"@DisabledIf(\"#{'enigma'}\") on " + method + " must evaluate to \"true\" or \"false\", not \"enigma\"");
 	}
 
 	@Test
@@ -103,14 +98,16 @@ class DisabledIfConditionTests {
 	void disabledWithDefaultReason() {
 		ConditionEvaluationResult result = condition.evaluateExecutionCondition(buildExtensionContext("defaultReason"));
 		assertThat(result.isDisabled()).isTrue();
-		assertThat(result.getReason().get()).endsWith("defaultReason() is disabled because @DisabledIf(\"#{1 + 1 eq 2}\") evaluated to true");
+		assertThat(result.getReason().get())
+			.endsWith("defaultReason() is disabled because @DisabledIf(\"#{1 + 1 eq 2}\") evaluated to true");
 	}
 
 	@Test
 	void notDisabledWithDefaultReason() {
 		ConditionEvaluationResult result = condition.evaluateExecutionCondition(buildExtensionContext("neverDisabledWithDefaultReason"));
 		assertThat(result.isDisabled()).isFalse();
-		assertThat(result.getReason().get()).endsWith("neverDisabledWithDefaultReason() is enabled because @DisabledIf(\"false\") did not evaluate to true");
+		assertThat(result.getReason().get())
+			.endsWith("neverDisabledWithDefaultReason() is enabled because @DisabledIf(\"false\") did not evaluate to true");
 	}
 
 	// -------------------------------------------------------------------------
@@ -129,10 +126,9 @@ class DisabledIfConditionTests {
 	}
 
 	private void assertExpressionIsBlank(String methodName) {
-		IllegalStateException exception = assertThrows(IllegalStateException.class,
-			() -> condition.evaluateExecutionCondition(buildExtensionContext(methodName)));
-
-		assertThat(exception.getMessage()).contains("must not be blank");
+		assertThatIllegalStateException()
+			.isThrownBy(() -> condition.evaluateExecutionCondition(buildExtensionContext(methodName)))
+			.withMessageContaining("must not be blank");
 	}
 
 	// -------------------------------------------------------------------------

spring-test/src/test/java/org/springframework/test/context/junit/jupiter/DisabledIfTests.java

@@ -24,8 +24,8 @@ import org.springframework.context.annotation.Configuration;
 import org.springframework.test.context.TestPropertySource;
 import org.springframework.test.context.junit.SpringJUnitJupiterTestSuite;
 
-import static org.junit.jupiter.api.Assertions.assertFalse;
-import static org.junit.jupiter.api.Assertions.fail;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.fail;
 
 /**
  * Integration tests which verify support for {@link DisabledIf @DisabledIf}
@@ -111,7 +111,8 @@ class DisabledIfTests {
 		@Test
 		@DisabledOnMac
 		void disabledIfWithSpelOsCheckInCustomComposedAnnotation() {
-			assertFalse(System.getProperty("os.name").contains("Mac"), "This test must be disabled on Mac OS");
+			String os = System.getProperty("os.name").toLowerCase();
+			assertThat(os).as("This test must be disabled on Mac OS").doesNotContain("mac");
 		}
 
 		@Test

spring-test/src/test/java/org/springframework/test/context/junit/jupiter/EnabledIfTests.java

@@ -24,9 +24,8 @@ import org.springframework.context.annotation.Configuration;
 import org.springframework.test.context.TestPropertySource;
 import org.springframework.test.context.junit.SpringJUnitJupiterTestSuite;
 
-import static org.junit.jupiter.api.Assertions.assertFalse;
-import static org.junit.jupiter.api.Assertions.assertTrue;
-import static org.junit.jupiter.api.Assertions.fail;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.fail;
 
 /**
  * Integration tests which verify support for {@link EnabledIf @EnabledIf}
@@ -113,8 +112,8 @@ class EnabledIfTests {
 		@EnabledOnMac
 		void enabledIfWithSpelOsCheckInCustomComposedAnnotation() {
 			String os = System.getProperty("os.name").toLowerCase();
-			assertTrue(os.contains("mac"), "This test must be enabled on Mac OS");
-			assertFalse(os.contains("win"), "This test must be disabled on Windows");
+			assertThat(os).as("This test must be enabled on Mac OS").contains("mac");
+			assertThat(os).as("This test must be disabled on Windows").doesNotContain("win");
 		}
 
 		@Test

spring-test/src/test/java/org/springframework/test/context/junit/jupiter/FailingBeforeAndAfterMethodsSpringExtensionTests.java

@@ -31,7 +31,6 @@ import org.junit.platform.launcher.TestIdentifier;
 import org.junit.platform.launcher.core.LauncherFactory;
 import org.junit.platform.launcher.listeners.SummaryGeneratingListener;
 import org.junit.platform.launcher.listeners.TestExecutionSummary;
-import org.opentest4j.AssertionFailedError;
 
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
@@ -46,9 +45,9 @@ import org.springframework.test.context.transaction.BeforeTransaction;
 import org.springframework.transaction.PlatformTransactionManager;
 import org.springframework.transaction.annotation.Transactional;
 
-import static org.junit.jupiter.api.Assertions.assertAll;
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.fail;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.fail;
+import static org.assertj.core.api.SoftAssertions.assertSoftly;
 import static org.junit.jupiter.api.DynamicTest.dynamicTest;
 import static org.junit.platform.engine.discovery.DiscoverySelectors.selectClass;
 import static org.junit.platform.launcher.core.LauncherDiscoveryRequestBuilder.request;
@@ -106,27 +105,20 @@ class FailingBeforeAndAfterMethodsSpringExtensionTests {
 		int expectedSucceededCount = getExpectedSucceededCount(testClass);
 		int expectedFailedCount = getExpectedFailedCount(testClass);
 
-		// @formatter:off
-		assertAll(
-			() -> assertEquals(1, summary.getTestsFoundCount(), () -> name + ": tests found"),
-			() -> assertEquals(0, summary.getTestsSkippedCount(), () -> name + ": tests skipped"),
-			() -> assertEquals(0, summary.getTestsAbortedCount(), () -> name + ": tests aborted"),
-			() -> assertEquals(expectedStartedCount, summary.getTestsStartedCount(), () -> name + ": tests started"),
-			() -> assertEquals(expectedSucceededCount, summary.getTestsSucceededCount(), () -> name + ": tests succeeded"),
-			() -> assertEquals(expectedFailedCount, summary.getTestsFailedCount(), () -> name + ": tests failed")
-		);
-		// @formatter:on
+		assertSoftly(softly -> {
+			softly.assertThat(summary.getTestsFoundCount()).as("%s: tests found", name).isEqualTo(1);
+			softly.assertThat(summary.getTestsSkippedCount()).as("%s: tests skipped", name).isEqualTo(0);
+			softly.assertThat(summary.getTestsAbortedCount()).as("%s: tests aborted", name).isEqualTo(0);
+			softly.assertThat(summary.getTestsStartedCount()).as("%s: tests started", name).isEqualTo(expectedStartedCount);
+			softly.assertThat(summary.getTestsSucceededCount()).as("%s: tests succeeded", name).isEqualTo(expectedSucceededCount);
+			softly.assertThat(summary.getTestsFailedCount()).as("%s: tests failed", name).isEqualTo(expectedFailedCount);
+		});
 
-		// Ensure it was an AssertionFailedError that failed the test and not
+		// Ensure it was an AssertionError that failed the test and not
 		// something else like an error in the @Configuration class, etc.
 		if (expectedFailedCount > 0) {
-			assertEquals(1, listener.exceptions.size(), "exceptions expected");
-			Throwable exception = listener.exceptions.get(0);
-			if (!(exception instanceof AssertionFailedError)) {
-				throw new AssertionFailedError(
-					exception.getClass().getName() + " is not an instance of " + AssertionFailedError.class.getName(),
-					exception);
-			}
+			assertThat(listener.exceptions).as("exceptions expected").hasSize(1);
+			assertThat(listener.exceptions.get(0)).isInstanceOf(AssertionError.class);
 		}
 	}
 

spring-test/src/test/java/org/springframework/test/context/junit/jupiter/RegisterExtensionSpringExtensionTests.java

@@ -36,11 +36,7 @@ import org.springframework.test.context.junit.jupiter.comics.Cat;
 import org.springframework.test.context.junit.jupiter.comics.Dog;
 import org.springframework.test.context.junit.jupiter.comics.Person;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertFalse;
-import static org.junit.jupiter.api.Assertions.assertNotNull;
-import static org.junit.jupiter.api.Assertions.assertNull;
-import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.assertj.core.api.Assertions.assertThat;
 
 /**
  * Integration tests which demonstrate that the Spring TestContext Framework can be used
@@ -82,56 +78,52 @@ class RegisterExtensionSpringExtensionTests {
 	@Value("${enigma}")
 	Integer enigma;
 
+
 	@Test
 	void applicationContextInjectedIntoMethod(ApplicationContext applicationContext) {
-		assertNotNull(applicationContext,
-				"ApplicationContext should have been injected by Spring");
-		assertEquals(this.dilbert, applicationContext.getBean("dilbert", Person.class));
+		assertThat(applicationContext).as("ApplicationContext should have been injected by Spring").isNotNull();
+		assertThat(applicationContext.getBean("dilbert", Person.class)).isEqualTo(this.dilbert);
 	}
 
 	@Test
-	void genericApplicationContextInjectedIntoMethod(
-			GenericApplicationContext applicationContext) {
-		assertNotNull(applicationContext,
-				"GenericApplicationContext should have been injected by Spring");
-		assertEquals(this.dilbert, applicationContext.getBean("dilbert", Person.class));
+	void genericApplicationContextInjectedIntoMethod(GenericApplicationContext applicationContext) {
+		assertThat(applicationContext).as("GenericApplicationContext should have been injected by Spring").isNotNull();
+		assertThat(applicationContext.getBean("dilbert", Person.class)).isEqualTo(this.dilbert);
 	}
 
 	@Test
 	void autowiredFields() {
-		assertNotNull(this.dilbert, "Dilbert should have been @Autowired by Spring");
-		assertEquals("Dilbert", this.dilbert.getName(), "Person's name");
-		assertEquals(2, this.people.size(), "Number of people in context");
+		assertThat(this.dilbert).as("Dilbert should have been @Autowired by Spring").isNotNull();
+		assertThat(this.dilbert.getName()).as("Person's name").isEqualTo("Dilbert");
+		assertThat(this.people).as("Number of people in context").hasSize(2);
 
-		assertNotNull(this.dog, "Dogbert should have been @Autowired by Spring");
-		assertEquals("Dogbert", this.dog.getName(), "Dog's name");
+		assertThat(this.dog).as("Dogbert should have been @Autowired by Spring").isNotNull();
+		assertThat(this.dog.getName()).as("Dog's name").isEqualTo("Dogbert");
 
-		assertNotNull(this.cat,
-				"Catbert should have been @Autowired by Spring as the @Primary cat");
-		assertEquals("Catbert", this.cat.getName(), "Primary cat's name");
-		assertEquals(2, this.cats.size(), "Number of cats in context");
+		assertThat(this.cat).as("Catbert should have been @Autowired by Spring as the @Primary cat").isNotNull();
+		assertThat(this.cat.getName()).as("Primary cat's name").isEqualTo("Catbert");
+		assertThat(this.cats).as("Number of cats in context").hasSize(2);
 
-		assertNotNull(this.enigma,
-				"Enigma should have been injected via @Value by Spring");
-		assertEquals(Integer.valueOf(42), this.enigma, "enigma");
+		assertThat(this.enigma).as("Enigma should have been injected via @Value by Spring").isNotNull();
+		assertThat(this.enigma).as("enigma").isEqualTo(42);
 	}
 
 	@Test
 	void autowiredParameterByTypeForSingleBean(@Autowired Dog dog) {
-		assertNotNull(dog, "Dogbert should have been @Autowired by Spring");
-		assertEquals("Dogbert", dog.getName(), "Dog's name");
+		assertThat(dog).as("Dogbert should have been @Autowired by Spring").isNotNull();
+		assertThat(dog.getName()).as("Dog's name").isEqualTo("Dogbert");
 	}
 
 	@Test
 	void autowiredParameterByTypeForPrimaryBean(@Autowired Cat primaryCat) {
-		assertNotNull(primaryCat, "Primary cat should have been @Autowired by Spring");
-		assertEquals("Catbert", primaryCat.getName(), "Primary cat's name");
+		assertThat(primaryCat).as("Primary cat should have been @Autowired by Spring").isNotNull();
+		assertThat(primaryCat.getName()).as("Primary cat's name").isEqualTo("Catbert");
 	}
 
 	@Test
 	void autowiredParameterWithExplicitQualifier(@Qualifier("wally") Person person) {
-		assertNotNull(person, "Wally should have been @Autowired by Spring");
-		assertEquals("Wally", person.getName(), "Person's name");
+		assertThat(person).as("Wally should have been @Autowired by Spring").isNotNull();
+		assertThat(person.getName()).as("Person's name").isEqualTo("Wally");
 	}
 
 	/**
@@ -140,85 +132,74 @@ class RegisterExtensionSpringExtensionTests {
 	 * {@code @Qualifier("wally")}.
 	 */
 	@Test
-	void autowiredParameterWithImplicitQualifierBasedOnParameterName(
-			@Autowired Person wally) {
-		assertNotNull(wally, "Wally should have been @Autowired by Spring");
-		assertEquals("Wally", wally.getName(), "Person's name");
+	void autowiredParameterWithImplicitQualifierBasedOnParameterName(@Autowired Person wally) {
+		assertThat(wally).as("Wally should have been @Autowired by Spring").isNotNull();
+		assertThat(wally.getName()).as("Person's name").isEqualTo("Wally");
 	}
 
 	@Test
 	void autowiredParameterAsJavaUtilOptional(@Autowired Optional<Dog> dog) {
-		assertNotNull(dog, "Optional dog should have been @Autowired by Spring");
-		assertTrue(dog.isPresent(), "Value of Optional should be 'present'");
-		assertEquals("Dogbert", dog.get().getName(), "Dog's name");
+		assertThat(dog).as("Optional dog should have been @Autowired by Spring").isNotNull();
+		assertThat(dog.isPresent()).as("Value of Optional should be 'present'").isTrue();
+		assertThat(dog.get().getName()).as("Dog's name").isEqualTo("Dogbert");
 	}
 
 	@Test
-	void autowiredParameterThatDoesNotExistAsJavaUtilOptional(
-			@Autowired Optional<Number> number) {
-		assertNotNull(number, "Optional number should have been @Autowired by Spring");
-		assertFalse(number.isPresent(),
-				"Value of Optional number should not be 'present'");
+	void autowiredParameterThatDoesNotExistAsJavaUtilOptional(@Autowired Optional<Number> number) {
+		assertThat(number).as("Optional number should have been @Autowired by Spring").isNotNull();
+		assertThat(number).as("Value of Optional number should not be 'present'").isNotPresent();
 	}
 
 	@Test
-	void autowiredParameterThatDoesNotExistButIsNotRequired(
-			@Autowired(required = false) Number number) {
-		assertNull(number,
-				"Non-required number should have been @Autowired as 'null' by Spring");
+	void autowiredParameterThatDoesNotExistButIsNotRequired(@Autowired(required = false) Number number) {
+		assertThat(number).as("Non-required number should have been @Autowired as 'null' by Spring").isNull();
 	}
 
 	@Test
 	void autowiredParameterOfList(@Autowired List<Person> peopleParam) {
-		assertNotNull(peopleParam,
-				"list of people should have been @Autowired by Spring");
-		assertEquals(2, peopleParam.size(), "Number of people in context");
+		assertThat(peopleParam).as("list of people should have been @Autowired by Spring").isNotNull();
+		assertThat(peopleParam).as("Number of people in context").hasSize(2);
 	}
 
 	@Test
 	void valueParameterWithPrimitiveType(@Value("99") int num) {
-		assertEquals(99, num);
+		assertThat(num).isEqualTo(99);
 	}
 
 	@Test
 	void valueParameterFromPropertyPlaceholder(@Value("${enigma}") Integer enigmaParam) {
-		assertNotNull(enigmaParam,
-				"Enigma should have been injected via @Value by Spring");
-		assertEquals(Integer.valueOf(42), enigmaParam, "enigma");
+		assertThat(enigmaParam).as("Enigma should have been injected via @Value by Spring").isNotNull();
+		assertThat(enigmaParam).as("enigma").isEqualTo(42);
 	}
 
 	@Test
-	void valueParameterFromDefaultValueForPropertyPlaceholder(
-			@Value("${bogus:false}") Boolean defaultValue) {
-		assertNotNull(defaultValue,
-				"Default value should have been injected via @Value by Spring");
-		assertEquals(false, defaultValue, "default value");
+	void valueParameterFromDefaultValueForPropertyPlaceholder(@Value("${bogus:false}") Boolean defaultValue) {
+		assertThat(defaultValue).as("Default value should have been injected via @Value by Spring").isNotNull();
+		assertThat(defaultValue).as("default value").isEqualTo(false);
 	}
 
 	@Test
 	void valueParameterFromSpelExpression(@Value("#{@dilbert.name}") String name) {
-		assertNotNull(name,
-				"Dilbert's name should have been injected via SpEL expression in @Value by Spring");
-		assertEquals("Dilbert", name, "name from SpEL expression");
+		assertThat(name).as(
+			"Dilbert's name should have been injected via SpEL expression in @Value by Spring").isNotNull();
+		assertThat(name).as("name from SpEL expression").isEqualTo("Dilbert");
 	}
 
 	@Test
-	void valueParameterFromSpelExpressionWithNestedPropertyPlaceholder(
-			@Value("#{'Hello ' + ${enigma}}") String hello) {
-		assertNotNull(hello,
-				"hello should have been injected via SpEL expression in @Value by Spring");
-		assertEquals("Hello 42", hello, "hello from SpEL expression");
+	void valueParameterFromSpelExpressionWithNestedPropertyPlaceholder(@Value("#{'Hello ' + ${enigma}}") String hello) {
+		assertThat(hello).as("hello should have been injected via SpEL expression in @Value by Spring").isNotNull();
+		assertThat(hello).as("hello from SpEL expression").isEqualTo("Hello 42");
 	}
 
 	@Test
-	void junitAndSpringMethodInjectionCombined(@Autowired Cat kittyCat, TestInfo testInfo,
-			ApplicationContext context, TestReporter testReporter) {
+	void junitAndSpringMethodInjectionCombined(@Autowired Cat kittyCat, TestInfo testInfo, ApplicationContext context,
+			TestReporter testReporter) {
 
-		assertNotNull(testInfo, "TestInfo should have been injected by JUnit");
-		assertNotNull(testReporter, "TestReporter should have been injected by JUnit");
+		assertThat(testInfo).as("TestInfo should have been injected by JUnit").isNotNull();
+		assertThat(testReporter).as("TestReporter should have been injected by JUnit").isNotNull();
 
-		assertNotNull(context, "ApplicationContext should have been injected by Spring");
-		assertNotNull(kittyCat, "Cat should have been @Autowired by Spring");
+		assertThat(context).as("ApplicationContext should have been injected by Spring").isNotNull();
+		assertThat(kittyCat).as("Cat should have been @Autowired by Spring").isNotNull();
 	}
 
 }

spring-test/src/test/java/org/springframework/test/context/junit/jupiter/SpringExtensionParameterizedTests.java

@@ -29,8 +29,7 @@ import org.springframework.test.context.junit.jupiter.comics.Cat;
 import org.springframework.test.context.junit.jupiter.comics.Dog;
 import org.springframework.test.context.junit.jupiter.comics.Person;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.assertj.core.api.Assertions.assertThat;
 
 /**
  * Integration tests which demonstrate that the Spring TestContext Framework
@@ -51,19 +50,19 @@ class SpringExtensionParameterizedTests {
 	@ParameterizedTest
 	@ValueSource(strings = { "Dilbert", "Wally" })
 	void people(String name, @Autowired List<Person> people) {
-		assertTrue(people.stream().map(Person::getName).filter(str -> name.equals(str)).findFirst().isPresent());
+		assertThat(people.stream().map(Person::getName).filter(name::equals)).size().isEqualTo(1);
 	}
 
 	@ParameterizedTest
 	@CsvSource("dogbert, Dogbert")
 	void dogs(String beanName, String dogName, ApplicationContext context) {
-		assertEquals(dogName, context.getBean(beanName, Dog.class).getName());
+		assertThat(context.getBean(beanName, Dog.class)).extracting(Dog::getName).isEqualTo(dogName);
 	}
 
 	@ParameterizedTest
 	@CsvSource({ "garfield, Garfield", "catbert, Catbert" })
 	void cats(String beanName, String catName, ApplicationContext context) {
-		assertEquals(catName, context.getBean(beanName, Cat.class).getName());
+		assertThat(context.getBean(beanName, Cat.class)).extracting(Cat::getName).isEqualTo(catName);
 	}
 
 }

spring-test/src/test/java/org/springframework/test/context/junit/jupiter/SpringExtensionTests.java

@@ -36,11 +36,7 @@ import org.springframework.test.context.junit.jupiter.comics.Cat;
 import org.springframework.test.context.junit.jupiter.comics.Dog;
 import org.springframework.test.context.junit.jupiter.comics.Person;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertFalse;
-import static org.junit.jupiter.api.Assertions.assertNotNull;
-import static org.junit.jupiter.api.Assertions.assertNull;
-import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.assertj.core.api.Assertions.assertThat;
 
 /**
  * Integration tests which demonstrate that the Spring TestContext Framework can
@@ -79,49 +75,49 @@ class SpringExtensionTests {
 
 	@Test
 	void applicationContextInjectedIntoMethod(ApplicationContext applicationContext) {
-		assertNotNull(applicationContext, "ApplicationContext should have been injected by Spring");
-		assertEquals(this.dilbert, applicationContext.getBean("dilbert", Person.class));
+		assertThat(applicationContext).as("ApplicationContext should have been injected by Spring").isNotNull();
+		assertThat(applicationContext.getBean("dilbert", Person.class)).isEqualTo(this.dilbert);
 	}
 
 	@Test
 	void genericApplicationContextInjectedIntoMethod(GenericApplicationContext applicationContext) {
-		assertNotNull(applicationContext, "GenericApplicationContext should have been injected by Spring");
-		assertEquals(this.dilbert, applicationContext.getBean("dilbert", Person.class));
+		assertThat(applicationContext).as("GenericApplicationContext should have been injected by Spring").isNotNull();
+		assertThat(applicationContext.getBean("dilbert", Person.class)).isEqualTo(this.dilbert);
 	}
 
 	@Test
 	void autowiredFields() {
-		assertNotNull(this.dilbert, "Dilbert should have been @Autowired by Spring");
-		assertEquals("Dilbert", this.dilbert.getName(), "Person's name");
-		assertEquals(2, this.people.size(), "Number of people in context");
+		assertThat(this.dilbert).as("Dilbert should have been @Autowired by Spring").isNotNull();
+		assertThat(this.dilbert.getName()).as("Person's name").isEqualTo("Dilbert");
+		assertThat(this.people).as("Number of people in context").hasSize(2);
 
-		assertNotNull(this.dog, "Dogbert should have been @Autowired by Spring");
-		assertEquals("Dogbert", this.dog.getName(), "Dog's name");
+		assertThat(this.dog).as("Dogbert should have been @Autowired by Spring").isNotNull();
+		assertThat(this.dog.getName()).as("Dog's name").isEqualTo("Dogbert");
 
-		assertNotNull(this.cat, "Catbert should have been @Autowired by Spring as the @Primary cat");
-		assertEquals("Catbert", this.cat.getName(), "Primary cat's name");
-		assertEquals(2, this.cats.size(), "Number of cats in context");
+		assertThat(this.cat).as("Catbert should have been @Autowired by Spring as the @Primary cat").isNotNull();
+		assertThat(this.cat.getName()).as("Primary cat's name").isEqualTo("Catbert");
+		assertThat(this.cats).as("Number of cats in context").hasSize(2);
 
-		assertNotNull(this.enigma, "Enigma should have been injected via @Value by Spring");
-		assertEquals(Integer.valueOf(42), this.enigma, "enigma");
+		assertThat(this.enigma).as("Enigma should have been injected via @Value by Spring").isNotNull();
+		assertThat(this.enigma).as("enigma").isEqualTo(42);
 	}
 
 	@Test
 	void autowiredParameterByTypeForSingleBean(@Autowired Dog dog) {
-		assertNotNull(dog, "Dogbert should have been @Autowired by Spring");
-		assertEquals("Dogbert", dog.getName(), "Dog's name");
+		assertThat(dog).as("Dogbert should have been @Autowired by Spring").isNotNull();
+		assertThat(dog.getName()).as("Dog's name").isEqualTo("Dogbert");
 	}
 
 	@Test
 	void autowiredParameterByTypeForPrimaryBean(@Autowired Cat primaryCat) {
-		assertNotNull(primaryCat, "Primary cat should have been @Autowired by Spring");
-		assertEquals("Catbert", primaryCat.getName(), "Primary cat's name");
+		assertThat(primaryCat).as("Primary cat should have been @Autowired by Spring").isNotNull();
+		assertThat(primaryCat.getName()).as("Primary cat's name").isEqualTo("Catbert");
 	}
 
 	@Test
 	void autowiredParameterWithExplicitQualifier(@Qualifier("wally") Person person) {
-		assertNotNull(person, "Wally should have been @Autowired by Spring");
-		assertEquals("Wally", person.getName(), "Person's name");
+		assertThat(person).as("Wally should have been @Autowired by Spring").isNotNull();
+		assertThat(person.getName()).as("Person's name").isEqualTo("Wally");
 	}
 
 	/**
@@ -131,72 +127,72 @@ class SpringExtensionTests {
 	 */
 	@Test
 	void autowiredParameterWithImplicitQualifierBasedOnParameterName(@Autowired Person wally) {
-		assertNotNull(wally, "Wally should have been @Autowired by Spring");
-		assertEquals("Wally", wally.getName(), "Person's name");
+		assertThat(wally).as("Wally should have been @Autowired by Spring").isNotNull();
+		assertThat(wally.getName()).as("Person's name").isEqualTo("Wally");
 	}
 
 	@Test
 	void autowiredParameterAsJavaUtilOptional(@Autowired Optional<Dog> dog) {
-		assertNotNull(dog, "Optional dog should have been @Autowired by Spring");
-		assertTrue(dog.isPresent(), "Value of Optional should be 'present'");
-		assertEquals("Dogbert", dog.get().getName(), "Dog's name");
+		assertThat(dog).as("Optional dog should have been @Autowired by Spring").isNotNull();
+		assertThat(dog).as("Value of Optional should be 'present'").isPresent();
+		assertThat(dog.get().getName()).as("Dog's name").isEqualTo("Dogbert");
 	}
 
 	@Test
 	void autowiredParameterThatDoesNotExistAsJavaUtilOptional(@Autowired Optional<Number> number) {
-		assertNotNull(number, "Optional number should have been @Autowired by Spring");
-		assertFalse(number.isPresent(), "Value of Optional number should not be 'present'");
+		assertThat(number).as("Optional number should have been @Autowired by Spring").isNotNull();
+		assertThat(number).as("Value of Optional number should not be 'present'").isNotPresent();
 	}
 
 	@Test
 	void autowiredParameterThatDoesNotExistButIsNotRequired(@Autowired(required = false) Number number) {
-		assertNull(number, "Non-required number should have been @Autowired as 'null' by Spring");
+		assertThat(number).as("Non-required number should have been @Autowired as 'null' by Spring").isNull();
 	}
 
 	@Test
 	void autowiredParameterOfList(@Autowired List<Person> peopleParam) {
-		assertNotNull(peopleParam, "list of people should have been @Autowired by Spring");
-		assertEquals(2, peopleParam.size(), "Number of people in context");
+		assertThat(peopleParam).as("list of people should have been @Autowired by Spring").isNotNull();
+		assertThat(peopleParam).as("Number of people in context").hasSize(2);
 	}
 
 	@Test
 	void valueParameterWithPrimitiveType(@Value("99") int num) {
-		assertEquals(99, num);
+		assertThat(num).isEqualTo(99);
 	}
 
 	@Test
 	void valueParameterFromPropertyPlaceholder(@Value("${enigma}") Integer enigmaParam) {
-		assertNotNull(enigmaParam, "Enigma should have been injected via @Value by Spring");
-		assertEquals(Integer.valueOf(42), enigmaParam, "enigma");
+		assertThat(enigmaParam).as("Enigma should have been injected via @Value by Spring").isNotNull();
+		assertThat(enigmaParam).as("enigma").isEqualTo(42);
 	}
 
 	@Test
 	void valueParameterFromDefaultValueForPropertyPlaceholder(@Value("${bogus:false}") Boolean defaultValue) {
-		assertNotNull(defaultValue, "Default value should have been injected via @Value by Spring");
-		assertEquals(false, defaultValue, "default value");
+		assertThat(defaultValue).as("Default value should have been injected via @Value by Spring").isNotNull();
+		assertThat(defaultValue).as("default value").isEqualTo(false);
 	}
 
 	@Test
 	void valueParameterFromSpelExpression(@Value("#{@dilbert.name}") String name) {
-		assertNotNull(name, "Dilbert's name should have been injected via SpEL expression in @Value by Spring");
-		assertEquals("Dilbert", name, "name from SpEL expression");
+		assertThat(name).as("Dilbert's name should have been injected via SpEL expression in @Value by Spring").isNotNull();
+		assertThat(name).as("name from SpEL expression").isEqualTo("Dilbert");
 	}
 
 	@Test
 	void valueParameterFromSpelExpressionWithNestedPropertyPlaceholder(@Value("#{'Hello ' + ${enigma}}") String hello) {
-		assertNotNull(hello, "hello should have been injected via SpEL expression in @Value by Spring");
-		assertEquals("Hello 42", hello, "hello from SpEL expression");
+		assertThat(hello).as("hello should have been injected via SpEL expression in @Value by Spring").isNotNull();
+		assertThat(hello).as("hello from SpEL expression").isEqualTo("Hello 42");
 	}
 
 	@Test
 	void junitAndSpringMethodInjectionCombined(@Autowired Cat kittyCat, TestInfo testInfo, ApplicationContext context,
 			TestReporter testReporter) {
 
-		assertNotNull(testInfo, "TestInfo should have been injected by JUnit");
-		assertNotNull(testReporter, "TestReporter should have been injected by JUnit");
+		assertThat(testInfo).as("TestInfo should have been injected by JUnit").isNotNull();
+		assertThat(testReporter).as("TestReporter should have been injected by JUnit").isNotNull();
 
-		assertNotNull(context, "ApplicationContext should have been injected by Spring");
-		assertNotNull(kittyCat, "Cat should have been @Autowired by Spring");
+		assertThat(context).as("ApplicationContext should have been injected by Spring").isNotNull();
+		assertThat(kittyCat).as("Cat should have been @Autowired by Spring").isNotNull();
 	}
 
 }

spring-test/src/test/java/org/springframework/test/context/junit/jupiter/SpringJUnitJupiterAutowiredConstructorInjectionTests.java

@@ -26,8 +26,7 @@ import org.springframework.test.context.junit.SpringJUnitJupiterTestSuite;
 import org.springframework.test.context.junit.jupiter.comics.Dog;
 import org.springframework.test.context.junit.jupiter.comics.Person;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.assertj.core.api.Assertions.assertThat;
 
 /**
  * Integration tests which demonstrate support for {@link Autowired @Autowired}
@@ -62,23 +61,23 @@ class SpringJUnitJupiterAutowiredConstructorInjectionTests {
 
 	@Test
 	void applicationContextInjected() {
-		assertNotNull(applicationContext, "ApplicationContext should have been injected by Spring");
-		assertEquals(this.dilbert, applicationContext.getBean("dilbert", Person.class));
+		assertThat(applicationContext).as("ApplicationContext should have been injected by Spring").isNotNull();
+		assertThat(applicationContext.getBean("dilbert", Person.class)).isEqualTo(this.dilbert);
 	}
 
 	@Test
 	void beansInjected() {
-		assertNotNull(this.dilbert, "Dilbert should have been @Autowired by Spring");
-		assertEquals("Dilbert", this.dilbert.getName(), "Person's name");
+		assertThat(this.dilbert).as("Dilbert should have been @Autowired by Spring").isNotNull();
+		assertThat(this.dilbert.getName()).as("Person's name").isEqualTo("Dilbert");
 
-		assertNotNull(this.dog, "Dogbert should have been @Autowired by Spring");
-		assertEquals("Dogbert", this.dog.getName(), "Dog's name");
+		assertThat(this.dog).as("Dogbert should have been @Autowired by Spring").isNotNull();
+		assertThat(this.dog.getName()).as("Dog's name").isEqualTo("Dogbert");
 	}
 
 	@Test
 	void propertyPlaceholderInjected() {
-		assertNotNull(this.enigma, "Enigma should have been injected via @Value by Spring");
-		assertEquals(Integer.valueOf(42), this.enigma, "enigma");
+		assertThat(this.enigma).as("Enigma should have been injected via @Value by Spring").isNotNull();
+		assertThat(this.enigma).as("enigma").isEqualTo(42);
 	}
 
 }

spring-test/src/test/java/org/springframework/test/context/junit/jupiter/SpringJUnitJupiterConstructorInjectionTests.java

@@ -27,8 +27,7 @@ import org.springframework.test.context.junit.SpringJUnitJupiterTestSuite;
 import org.springframework.test.context.junit.jupiter.comics.Dog;
 import org.springframework.test.context.junit.jupiter.comics.Person;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.assertj.core.api.Assertions.assertThat;
 
 /**
  * Integration tests which demonstrate support for autowiring individual
@@ -65,28 +64,28 @@ class SpringJUnitJupiterConstructorInjectionTests {
 
 	@Test
 	void applicationContextInjected() {
-		assertNotNull(applicationContext, "ApplicationContext should have been injected by Spring");
-		assertEquals(this.dilbert, applicationContext.getBean("dilbert", Person.class));
+		assertThat(applicationContext).as("ApplicationContext should have been injected by Spring").isNotNull();
+		assertThat(applicationContext.getBean("dilbert", Person.class)).isEqualTo(this.dilbert);
 	}
 
 	@Test
 	void beansInjected() {
-		assertNotNull(this.dilbert, "Dilbert should have been @Autowired by Spring");
-		assertEquals("Dilbert", this.dilbert.getName(), "Person's name");
+		assertThat(this.dilbert).as("Dilbert should have been @Autowired by Spring").isNotNull();
+		assertThat(this.dilbert.getName()).as("Person's name").isEqualTo("Dilbert");
 
-		assertNotNull(this.dog, "Dogbert should have been @Autowired by Spring");
-		assertEquals("Dogbert", this.dog.getName(), "Dog's name");
+		assertThat(this.dog).as("Dogbert should have been @Autowired by Spring").isNotNull();
+		assertThat(this.dog.getName()).as("Dog's name").isEqualTo("Dogbert");
 	}
 
 	@Test
 	void propertyPlaceholderInjected() {
-		assertNotNull(this.enigma, "Enigma should have been injected via @Value by Spring");
-		assertEquals(Integer.valueOf(42), this.enigma, "enigma");
+		assertThat(this.enigma).as("Enigma should have been injected via @Value by Spring").isNotNull();
+		assertThat(this.enigma).as("enigma").isEqualTo(42);
 	}
 
 	@Test
 	void testInfoInjected() {
-		assertNotNull(this.testInfo, "TestInfo should have been injected by JUnit");
+		assertThat(this.testInfo).as("TestInfo should have been injected by JUnit").isNotNull();
 	}
 
 }

spring-test/src/test/java/org/springframework/test/context/junit/jupiter/SpringManagedJupiterExtensionTests.java

@@ -35,7 +35,7 @@ import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 
-import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.assertj.core.api.Assertions.assertThat;
 
 /**
  * This class demonstrates how to have a JUnit Jupiter extension managed as a
@@ -56,7 +56,7 @@ class SpringManagedJupiterExtensionTests {
 
 	@TestTemplate
 	void testTemplate(String parameter) {
-		assertTrue("foo".equals(parameter) || "bar".equals(parameter));
+		assertThat("foo".equals(parameter) || "bar".equals(parameter)).isTrue();
 	}
 
 

spring-test/src/test/java/org/springframework/test/context/junit/jupiter/TestConstructorAnnotationIntegrationTests.java

@@ -27,8 +27,7 @@ import org.springframework.test.context.junit.SpringJUnitJupiterTestSuite;
 import org.springframework.test.context.junit.jupiter.comics.Dog;
 import org.springframework.test.context.junit.jupiter.comics.Person;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.assertj.core.api.Assertions.assertThat;
 
 /**
  * Integration tests which demonstrate support for automatically
@@ -65,23 +64,23 @@ class TestConstructorAnnotationIntegrationTests {
 
 	@Test
 	void applicationContextInjected() {
-		assertNotNull(applicationContext, "ApplicationContext should have been injected by Spring");
-		assertEquals(this.dilbert, applicationContext.getBean("dilbert", Person.class));
+		assertThat(applicationContext).as("ApplicationContext should have been injected by Spring").isNotNull();
+		assertThat(applicationContext.getBean("dilbert", Person.class)).isEqualTo(this.dilbert);
 	}
 
 	@Test
 	void beansInjected() {
-		assertNotNull(this.dilbert, "Dilbert should have been @Autowired by Spring");
-		assertEquals("Dilbert", this.dilbert.getName(), "Person's name");
+		assertThat(this.dilbert).as("Dilbert should have been @Autowired by Spring").isNotNull();
+		assertThat(this.dilbert.getName()).as("Person's name").isEqualTo("Dilbert");
 
-		assertNotNull(this.dog, "Dogbert should have been @Autowired by Spring");
-		assertEquals("Dogbert", this.dog.getName(), "Dog's name");
+		assertThat(this.dog).as("Dogbert should have been @Autowired by Spring").isNotNull();
+		assertThat(this.dog.getName()).as("Dog's name").isEqualTo("Dogbert");
 	}
 
 	@Test
 	void propertyPlaceholderInjected() {
-		assertNotNull(this.enigma, "Enigma should have been injected via @Value by Spring");
-		assertEquals(Integer.valueOf(42), this.enigma, "enigma");
+		assertThat(this.enigma).as("Enigma should have been injected via @Value by Spring").isNotNull();
+		assertThat(this.enigma).as("enigma").isEqualTo(42);
 	}
 
 }

spring-test/src/test/java/org/springframework/test/context/junit/jupiter/defaultmethods/GenericComicCharactersInterfaceDefaultMethodsTests.java

@@ -27,8 +27,7 @@ import org.springframework.test.context.junit.jupiter.SpringJUnitConfig;
 import org.springframework.test.context.junit.jupiter.TestConfig;
 import org.springframework.test.context.junit.jupiter.comics.Character;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.assertj.core.api.Assertions.assertThat;
 
 /**
  * Interface for integration tests that demonstrate support for interface default
@@ -46,13 +45,13 @@ interface GenericComicCharactersInterfaceDefaultMethodsTests<C extends Character
 
 	@Test
 	default void autowiredParameterWithParameterizedList(@Autowired List<C> characters) {
-		assertEquals(getExpectedNumCharacters(), characters.size(), "Number of characters in context");
+		assertThat(characters).as("Number of characters in context").size().isEqualTo(getExpectedNumCharacters());
 	}
 
 	@Test
 	default void autowiredParameterWithGenericBean(@Autowired C character) {
-		assertNotNull(character, "Character should have been @Autowired by Spring");
-		assertEquals(getExpectedName(), character.getName(), "character's name");
+		assertThat(character).as("Character should have been @Autowired by Spring").isNotNull();
+		assertThat(character).as("character's name").extracting(Character::getName).isEqualTo(getExpectedName());
 	}
 
 	int getExpectedNumCharacters();

spring-test/src/test/java/org/springframework/test/context/junit/jupiter/generics/GenericComicCharactersTests.java

@@ -27,8 +27,7 @@ import org.springframework.test.context.junit.jupiter.SpringJUnitConfig;
 import org.springframework.test.context.junit.jupiter.TestConfig;
 import org.springframework.test.context.junit.jupiter.comics.Character;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.assertj.core.api.Assertions.assertThat;
 
 /**
  * Abstract base class for integration tests that demonstrate support for
@@ -52,15 +51,15 @@ abstract class GenericComicCharactersTests<T extends Character> {
 
 	@Test
 	void autowiredFields() {
-		assertNotNull(this.character, "Character should have been @Autowired by Spring");
-		assertEquals(getExpectedName(), character.getName(), "character's name");
-		assertEquals(getExpectedNumCharacters(), this.characters.size(), "Number of characters in context");
+		assertThat(this.character).as("Character should have been @Autowired by Spring").isNotNull();
+		assertThat(this.character).as("character's name").extracting(Character::getName).isEqualTo(getExpectedName());
+		assertThat(this.characters).as("Number of characters in context").size().isEqualTo(getExpectedNumCharacters());
 	}
 
 	@Test
 	void autowiredParameterByTypeForSingleGenericBean(@Autowired T character) {
-		assertNotNull(character, "Character should have been @Autowired by Spring");
-		assertEquals(getExpectedName(), character.getName(), "character's name");
+		assertThat(character).as("Character should have been @Autowired by Spring").isNotNull();
+		assertThat(this.character).as("character's name").extracting(Character::getName).isEqualTo(getExpectedName());
 	}
 
 	abstract int getExpectedNumCharacters();

spring-test/src/test/java/org/springframework/test/context/junit/jupiter/nested/NestedTestsWithConstructorInjectionWithSpringAndJUnitJupiterTests.java

@@ -30,7 +30,7 @@ import org.springframework.test.context.junit.jupiter.SpringExtension;
 import org.springframework.test.context.junit.jupiter.SpringJUnitConfig;
 import org.springframework.test.context.junit.jupiter.nested.NestedTestsWithConstructorInjectionWithSpringAndJUnitJupiterTests.TopLevelConfig;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.assertj.core.api.Assertions.assertThat;
 
 /**
  * Integration tests that verify support for {@code @Nested} test classes in conjunction
@@ -57,7 +57,7 @@ class NestedTestsWithConstructorInjectionWithSpringAndJUnitJupiterTests {
 
 	@Test
 	void topLevelTest() {
-		assertEquals("foo", foo);
+		assertThat(foo).isEqualTo("foo");
 	}
 
 	@Nested
@@ -73,8 +73,8 @@ class NestedTestsWithConstructorInjectionWithSpringAndJUnitJupiterTests {
 
 		@Test
 		void nestedTest() throws Exception {
-			assertEquals("foo", foo);
-			assertEquals("bar", bar);
+			assertThat(foo).isEqualTo("foo");
+			assertThat(bar).isEqualTo("bar");
 		}
 	}
 
@@ -90,8 +90,8 @@ class NestedTestsWithConstructorInjectionWithSpringAndJUnitJupiterTests {
 
 		@Test
 		void nestedTest() throws Exception {
-			assertEquals("foo", foo);
-			assertEquals("bar", bar);
+			assertThat(foo).isEqualTo("foo");
+			assertThat(bar).isEqualTo("bar");
 		}
 	}
 
@@ -107,8 +107,8 @@ class NestedTestsWithConstructorInjectionWithSpringAndJUnitJupiterTests {
 
 		@Test
 		void nestedTest() throws Exception {
-			assertEquals("foo", foo);
-			assertEquals("bar", bar);
+			assertThat(foo).isEqualTo("foo");
+			assertThat(bar).isEqualTo("bar");
 		}
 	}
 
@@ -126,9 +126,9 @@ class NestedTestsWithConstructorInjectionWithSpringAndJUnitJupiterTests {
 
 		@Test
 		void nestedTest() throws Exception {
-			assertEquals("foo", foo);
-			assertEquals("bar", bar);
-			assertEquals(42, answer);
+			assertThat(foo).isEqualTo("foo");
+			assertThat(bar).isEqualTo("bar");
+			assertThat(answer).isEqualTo(42);
 		}
 	}
 

spring-test/src/test/java/org/springframework/test/context/junit/jupiter/nested/NestedTestsWithSpringAndJUnitJupiterTests.java

@@ -27,7 +27,7 @@ import org.springframework.test.context.junit.jupiter.SpringExtension;
 import org.springframework.test.context.junit.jupiter.SpringJUnitConfig;
 import org.springframework.test.context.junit.jupiter.nested.NestedTestsWithSpringAndJUnitJupiterTests.TopLevelConfig;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.assertj.core.api.Assertions.assertThat;
 
 /**
  * Integration tests that verify support for {@code @Nested} test classes
@@ -50,7 +50,7 @@ class NestedTestsWithSpringAndJUnitJupiterTests {
 
 	@Test
 	void topLevelTest() {
-		assertEquals("foo", foo);
+		assertThat(foo).isEqualTo("foo");
 	}
 
 
@@ -67,8 +67,8 @@ class NestedTestsWithSpringAndJUnitJupiterTests {
 			// In contrast to nested test classes running in JUnit 4, the foo
 			// field in the outer instance should have been injected from the
 			// test ApplicationContext for the outer instance.
-			assertEquals("foo", foo);
-			assertEquals("bar", bar);
+			assertThat(foo).isEqualTo("foo");
+			assertThat(bar).isEqualTo("bar");
 		}
 	}
 

spring-test/src/test/java/org/springframework/test/context/junit/jupiter/nested/NestedTestsWithSqlScriptsAndJUnitJupiterTests.java

@@ -32,7 +32,7 @@ import org.springframework.test.context.transaction.BeforeTransaction;
 import org.springframework.test.jdbc.JdbcTestUtils;
 import org.springframework.transaction.annotation.Transactional;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.assertj.core.api.Assertions.assertThat;
 
 /**
  * Integration tests that verify support for {@link Nested @Nested} test classes in
@@ -53,13 +53,13 @@ class NestedTestsWithSqlScriptsAndJUnitJupiterTests {
 	@BeforeTransaction
 	@AfterTransaction
 	void checkInitialDatabaseState() {
-		assertEquals(0, countRowsInTable("user"));
+		assertThat(countRowsInTable("user")).isEqualTo(0);
 	}
 
 	@Test
 	@Sql("/org/springframework/test/context/jdbc/data.sql")
 	void sqlScripts() {
-		assertEquals(1, countRowsInTable("user"));
+		assertThat(countRowsInTable("user")).isEqualTo(1);
 	}
 
 	private int countRowsInTable(String tableName) {
@@ -77,13 +77,13 @@ class NestedTestsWithSqlScriptsAndJUnitJupiterTests {
 		@BeforeTransaction
 		@AfterTransaction
 		void checkInitialDatabaseState() {
-			assertEquals(0, countRowsInTable("user"));
+			assertThat(countRowsInTable("user")).isEqualTo(0);
 		}
 
 		@Test
 		@Sql("/org/springframework/test/context/jdbc/data.sql")
 		void nestedSqlScripts() {
-			assertEquals(1, countRowsInTable("user"));
+			assertThat(countRowsInTable("user")).isEqualTo(1);
 		}
 
 		private int countRowsInTable(String tableName) {

spring-test/src/test/java/org/springframework/test/context/junit/jupiter/parallel/ParallelExecutionSpringExtensionTests.java

@@ -31,7 +31,7 @@ import org.springframework.context.ApplicationContext;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.test.context.junit.jupiter.SpringJUnitConfig;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.platform.engine.discovery.DiscoverySelectors.selectClass;
 import static org.junit.platform.launcher.core.LauncherDiscoveryRequestBuilder.request;
 
@@ -61,8 +61,8 @@ class ParallelExecutionSpringExtensionTests {
 
 		launcher.execute(request);
 
-		assertEquals(NUM_TESTS, listener.getSummary().getTestsSucceededCount(),
-				"number of tests executed successfully");
+		assertThat(listener.getSummary().getTestsSucceededCount()).as(
+			"number of tests executed successfully").isEqualTo(NUM_TESTS);
 	}
 
 	@SpringJUnitConfig

spring-test/src/test/java/org/springframework/test/context/junit4/JUnitTestingUtils.java

@@ -19,7 +19,6 @@ package org.springframework.test.context.junit4;
 import java.lang.reflect.Constructor;
 
 import org.junit.experimental.ParallelComputer;
-import org.junit.jupiter.api.Assertions;
 import org.junit.runner.Computer;
 import org.junit.runner.JUnitCore;
 import org.junit.runner.RunWith;
@@ -28,16 +27,11 @@ import org.junit.runner.notification.RunNotifier;
 
 import org.springframework.beans.BeanUtils;
 
-import static org.junit.jupiter.api.Assertions.assertAll;
-import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.assertj.core.api.SoftAssertions.assertSoftly;
 
 /**
  * Collection of utilities for testing the execution of JUnit 4 based tests.
  *
- * <p>Note that these utilities use {@link Assertions} from JUnit Jupiter,
- * but that should not result in any adverse side effects in terms of
- * proper test failure for failed assertions.
- *
  * @author Sam Brannen
  * @since 4.2
  * @see TrackingRunListener
@@ -101,15 +95,18 @@ public class JUnitTestingUtils {
 			junit.run(testClass);
 		}
 
-		// @formatter:off
-		assertAll(
-			() -> assertEquals(expectedStartedCount, listener.getTestStartedCount(), "tests started for [" + testClass + "]"),
-			() -> assertEquals(expectedFailedCount, listener.getTestFailureCount(), "tests failed for [" + testClass + "]"),
-			() -> assertEquals(expectedFinishedCount, listener.getTestFinishedCount(), "tests finished for [" + testClass + "]"),
-			() -> assertEquals(expectedIgnoredCount, listener.getTestIgnoredCount(), "tests ignored for [" + testClass + "]"),
-			() -> assertEquals(expectedAssumptionFailedCount, listener.getTestAssumptionFailureCount(), "failed assumptions for [" + testClass + "]")
-		);
-		// @formatter:on
+		assertSoftly(softly -> {
+			softly.assertThat(listener.getTestStartedCount()).as("tests started for [%s]", testClass)
+				.isEqualTo(expectedStartedCount);
+			softly.assertThat(listener.getTestFailureCount()).as("tests failed for [%s]", testClass)
+				.isEqualTo(expectedFailedCount);
+			softly.assertThat(listener.getTestFinishedCount()).as("tests finished for [%s]", testClass)
+				.isEqualTo(expectedFinishedCount);
+			softly.assertThat(listener.getTestIgnoredCount()).as("tests ignored for [%s]", testClass)
+				.isEqualTo(expectedIgnoredCount);
+			softly.assertThat(listener.getTestAssumptionFailureCount()).as("failed assumptions for [%s]", testClass)
+				.isEqualTo(expectedAssumptionFailedCount);
+		});
 	}
 
 	/**
@@ -140,15 +137,13 @@ public class JUnitTestingUtils {
 		junit.addListener(listener);
 		junit.run(computer, testClasses);
 
-		// @formatter:off
-		assertAll(
-			() -> assertEquals(expectedStartedCount, listener.getTestStartedCount(), "tests started"),
-			() -> assertEquals(expectedFailedCount, listener.getTestFailureCount(), "tests failed"),
-			() -> assertEquals(expectedFinishedCount, listener.getTestFinishedCount(), "tests finished"),
-			() -> assertEquals(expectedIgnoredCount, listener.getTestIgnoredCount(), "tests ignored"),
-			() -> assertEquals(expectedAssumptionFailedCount, listener.getTestAssumptionFailureCount(), "failed assumptions")
-		);
-		// @formatter:on
+		assertSoftly(softly -> {
+			softly.assertThat(listener.getTestStartedCount()).as("tests started]").isEqualTo(expectedStartedCount);
+			softly.assertThat(listener.getTestFailureCount()).as("tests failed]").isEqualTo(expectedFailedCount);
+			softly.assertThat(listener.getTestFinishedCount()).as("tests finished]").isEqualTo(expectedFinishedCount);
+			softly.assertThat(listener.getTestIgnoredCount()).as("tests ignored]").isEqualTo(expectedIgnoredCount);
+			softly.assertThat(listener.getTestAssumptionFailureCount()).as("failed assumptions]").isEqualTo(expectedAssumptionFailedCount);
+		});
 	}
 
 }

spring-test/src/test/java/org/springframework/test/web/client/match/MockRestRequestMatchersTests.java

@@ -25,9 +25,8 @@ import org.junit.Test;
 import org.springframework.http.HttpMethod;
 import org.springframework.mock.http.client.MockClientHttpRequest;
 
-import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
 import static org.hamcrest.Matchers.containsString;
-import static org.junit.jupiter.api.Assertions.assertThrows;
 
 /**
  * Unit tests for {@link MockRestRequestMatchers}.
@@ -59,8 +58,9 @@ public class MockRestRequestMatchersTests {
 	public void requestToNoMatch() throws Exception {
 		this.request.setURI(new URI("http://www.foo.com/bar"));
 
-		assertThrows(AssertionError.class,
-				() -> MockRestRequestMatchers.requestTo("http://www.foo.com/wrong").match(this.request));
+		assertThatThrownBy(
+			() -> MockRestRequestMatchers.requestTo("http://www.foo.com/wrong").match(this.request))
+				.isInstanceOf(AssertionError.class);
 	}
 
 	@Test
@@ -81,9 +81,9 @@ public class MockRestRequestMatchersTests {
 	public void methodNoMatch() throws Exception {
 		this.request.setMethod(HttpMethod.POST);
 
-		AssertionError error = assertThrows(AssertionError.class,
-				() -> MockRestRequestMatchers.method(HttpMethod.GET).match(this.request));
-		assertThat(error.getMessage()).contains("expected:<GET> but was:<POST>");
+		assertThatThrownBy(() -> MockRestRequestMatchers.method(HttpMethod.GET).match(this.request))
+			.isInstanceOf(AssertionError.class)
+			.hasMessageContaining("expected:<GET> but was:<POST>");
 	}
 
 	@Test
@@ -95,18 +95,18 @@ public class MockRestRequestMatchersTests {
 
 	@Test
 	public void headerMissing() throws Exception {
-		AssertionError error = assertThrows(AssertionError.class,
-				() -> MockRestRequestMatchers.header("foo", "bar").match(this.request));
-		assertThat(error.getMessage()).contains("was null");
+		assertThatThrownBy(() -> MockRestRequestMatchers.header("foo", "bar").match(this.request))
+			.isInstanceOf(AssertionError.class)
+			.hasMessageContaining("was null");
 	}
 
 	@Test
 	public void headerMissingValue() throws Exception {
 		this.request.getHeaders().put("foo", Arrays.asList("bar", "baz"));
 
-		AssertionError error = assertThrows(AssertionError.class,
-				() -> MockRestRequestMatchers.header("foo", "bad").match(this.request));
-		assertThat(error.getMessage()).contains("expected:<bad> but was:<bar>");
+		assertThatThrownBy(() -> MockRestRequestMatchers.header("foo", "bad").match(this.request))
+			.isInstanceOf(AssertionError.class)
+			.hasMessageContaining("expected:<bad> but was:<bar>");
 	}
 
 	@Test
@@ -118,18 +118,18 @@ public class MockRestRequestMatchersTests {
 
 	@Test
 	public void headerContainsWithMissingHeader() throws Exception {
-		AssertionError error = assertThrows(AssertionError.class,
-				() -> MockRestRequestMatchers.header("foo", containsString("baz")).match(this.request));
-		assertThat(error.getMessage()).contains("but was null");
+		assertThatThrownBy(() -> MockRestRequestMatchers.header("foo", containsString("baz")).match(this.request))
+			.isInstanceOf(AssertionError.class)
+			.hasMessageContaining("but was null");
 	}
 
 	@Test
 	public void headerContainsWithMissingValue() throws Exception {
 		this.request.getHeaders().put("foo", Arrays.asList("bar", "baz"));
 
-		AssertionError error = assertThrows(AssertionError.class,
-				() -> MockRestRequestMatchers.header("foo", containsString("bx")).match(this.request));
-		assertThat(error.getMessage()).contains("was \"bar\"");
+		assertThatThrownBy(() -> MockRestRequestMatchers.header("foo", containsString("bx")).match(this.request))
+			.isInstanceOf(AssertionError.class)
+			.hasMessageContaining("was \"bar\"");
 	}
 
 	@Test
@@ -141,18 +141,18 @@ public class MockRestRequestMatchersTests {
 
 	@Test
 	public void headersWithMissingHeader() throws Exception {
-		AssertionError error = assertThrows(AssertionError.class,
-				() -> MockRestRequestMatchers.header("foo", "bar").match(this.request));
-		assertThat(error.getMessage()).contains("but was null");
+		assertThatThrownBy(() -> MockRestRequestMatchers.header("foo", "bar").match(this.request))
+			.isInstanceOf(AssertionError.class)
+			.hasMessageContaining("but was null");
 	}
 
 	@Test
 	public void headersWithMissingValue() throws Exception {
 		this.request.getHeaders().put("foo", Collections.singletonList("bar"));
 
-		AssertionError error = assertThrows(AssertionError.class,
-				() -> MockRestRequestMatchers.header("foo", "bar", "baz").match(this.request));
-		assertThat(error.getMessage()).contains("to have at least <2> values");
+		assertThatThrownBy(() -> MockRestRequestMatchers.header("foo", "bar", "baz").match(this.request))
+			.isInstanceOf(AssertionError.class)
+			.hasMessageContaining("to have at least <2> values");
 	}
 
 	@Test
@@ -166,18 +166,18 @@ public class MockRestRequestMatchersTests {
 	public void queryParamMissing() throws Exception {
 		this.request.setURI(new URI("http://www.foo.com/a"));
 
-		AssertionError error = assertThrows(AssertionError.class,
-				() -> MockRestRequestMatchers.queryParam("foo", "bar").match(this.request));
-		assertThat(error.getMessage()).contains("but was null");
+		assertThatThrownBy(() -> MockRestRequestMatchers.queryParam("foo", "bar").match(this.request))
+			.isInstanceOf(AssertionError.class)
+			.hasMessageContaining("but was null");
 	}
 
 	@Test
 	public void queryParamMissingValue() throws Exception {
 		this.request.setURI(new URI("http://www.foo.com/a?foo=bar&foo=baz"));
 
-		AssertionError error = assertThrows(AssertionError.class,
-				() -> MockRestRequestMatchers.queryParam("foo", "bad").match(this.request));
-		assertThat(error.getMessage()).contains("expected:<bad> but was:<bar>");
+		assertThatThrownBy(() -> MockRestRequestMatchers.queryParam("foo", "bad").match(this.request))
+			.isInstanceOf(AssertionError.class)
+			.hasMessageContaining("expected:<bad> but was:<bar>");
 	}
 
 	@Test
@@ -191,9 +191,9 @@ public class MockRestRequestMatchersTests {
 	public void queryParamContainsWithMissingValue() throws Exception {
 		this.request.setURI(new URI("http://www.foo.com/a?foo=bar&foo=baz"));
 
-		AssertionError error = assertThrows(AssertionError.class,
-				() -> MockRestRequestMatchers.queryParam("foo", containsString("bx")).match(this.request));
-		assertThat(error.getMessage()).contains("was \"bar\"");
+		assertThatThrownBy(() -> MockRestRequestMatchers.queryParam("foo", containsString("bx")).match(this.request))
+			.isInstanceOf(AssertionError.class)
+			.hasMessageContaining("was \"bar\"");
 	}
 
 }

src/checkstyle/checkstyle.xml

@@ -98,7 +98,7 @@
 			<property name="id" value="bannedImports"/>
 			<property name="regexp" value="true" />
 			<property name="illegalClasses"
-				value="^reactor\.core\.support\.Assert,^junit\.framework\..+,^org\.junit\.Assert$,^org\.junit\.Assume$,^org\.junit\.Assert\.assertThat,^org\.junit\.Assume\.assumeThat,^org\.junit\.rules\.ExpectedException,^org\.slf4j\.LoggerFactory" />
+				value="^reactor\.core\.support\.Assert,^junit\.framework\..+,^org\.junit\.Assert$,^org\.junit\.Assume$,^org\.junit\.jupiter\.api\.Assertions$,^org\.junit\.Assert\.assertThat,^org\.junit\.Assume\.assumeThat,^org\.junit\.rules\.ExpectedException,^org\.slf4j\.LoggerFactory" />
 		</module>
 		<module name="com.puppycrawl.tools.checkstyle.checks.imports.IllegalImportCheck">
 			<property name="id" value="bannedHamcrestImports"/>
@@ -177,15 +177,21 @@
 			<property name="id" value="expectedExceptionAnnotation"/>
 			<property name="maximum" value="0"/>
 			<property name="format" value="\@Test\(expected" />
-			<property name="message"
-				value="Please use AssertJ asserThat." />
+			<property name="message" value="Please use AssertJ assertions." />
 			<property name="ignoreComments" value="true" />
 		</module>
 		<module name="com.puppycrawl.tools.checkstyle.checks.regexp.RegexpSinglelineJavaCheck">
+			<property name="id" value="junit4Assertions"/>
 			<property name="maximum" value="0"/>
 			<property name="format" value="org\.junit\.Assert\.assert" />
-			<property name="message"
-				value="Please use AssertJ imports." />
+			<property name="message" value="Please use AssertJ assertions." />
+			<property name="ignoreComments" value="true" />
+		</module>
+		<module name="com.puppycrawl.tools.checkstyle.checks.regexp.RegexpSinglelineJavaCheck">
+			<property name="id" value="junitJupiterAssertions"/>
+			<property name="maximum" value="0"/>
+			<property name="format" value="org\.junit\.jupiter\.api\.Assertions\.assert" />
+			<property name="message" value="Please use AssertJ assertions." />
 			<property name="ignoreComments" value="true" />
 		</module>