Add nullability annotations to tests in core/spring-boot-test

See gh-47263

core/spring-boot-test/build.gradle

@@ -62,3 +62,6 @@ dependencies {
 	testRuntimeOnly("org.junit.vintage:junit-vintage-engine")
 }
 
+tasks.named("compileTestJava") {
+	options.nullability.checking = "tests"
+}

core/spring-boot-test/src/test/java/org/springframework/boot/test/context/AnnotatedClassFinderTests.java

@@ -35,12 +35,14 @@ class AnnotatedClassFinderTests {
 	private final AnnotatedClassFinder finder = new AnnotatedClassFinder(SpringBootConfiguration.class);
 
 	@Test
+	@SuppressWarnings("NullAway") // Test null check
 	void findFromClassWhenSourceIsNullShouldThrowException() {
 		assertThatIllegalArgumentException().isThrownBy(() -> this.finder.findFromClass((Class<?>) null))
 			.withMessageContaining("'source' must not be null");
 	}
 
 	@Test
+	@SuppressWarnings("NullAway") // Test null check
 	void findFromPackageWhenSourceIsNullShouldThrowException() {
 		assertThatIllegalArgumentException().isThrownBy(() -> this.finder.findFromPackage((String) null))
 			.withMessageContaining("'source' must not be null");

core/spring-boot-test/src/test/java/org/springframework/boot/test/context/AnnotationsPropertySourceTests.java

@@ -41,6 +41,7 @@ import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException
 class AnnotationsPropertySourceTests {
 
 	@Test
+	@SuppressWarnings("NullAway") // Test null check
 	void createWhenSourceIsNullShouldThrowException() {
 		assertThatIllegalArgumentException().isThrownBy(() -> new AnnotationsPropertySource(null))
 			.withMessageContaining("Property source must not be null");

core/spring-boot-test/src/test/java/org/springframework/boot/test/context/ImportsContextCustomizerFactoryTests.java

@@ -18,6 +18,7 @@ package org.springframework.boot.test.context;
 
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
+import java.util.Collections;
 
 import org.junit.jupiter.api.Test;
 
@@ -46,29 +47,35 @@ class ImportsContextCustomizerFactoryTests {
 
 	@Test
 	void getContextCustomizerWhenHasNoImportAnnotationShouldReturnNull() {
-		ContextCustomizer customizer = this.factory.createContextCustomizer(TestWithNoImport.class, null);
+		ContextCustomizer customizer = this.factory.createContextCustomizer(TestWithNoImport.class,
+				Collections.emptyList());
 		assertThat(customizer).isNull();
 	}
 
 	@Test
 	void getContextCustomizerWhenHasImportAnnotationShouldReturnCustomizer() {
-		ContextCustomizer customizer = this.factory.createContextCustomizer(TestWithImport.class, null);
+		ContextCustomizer customizer = this.factory.createContextCustomizer(TestWithImport.class,
+				Collections.emptyList());
 		assertThat(customizer).isNotNull();
 	}
 
 	@Test
 	void getContextCustomizerWhenHasMetaImportAnnotationShouldReturnCustomizer() {
-		ContextCustomizer customizer = this.factory.createContextCustomizer(TestWithMetaImport.class, null);
+		ContextCustomizer customizer = this.factory.createContextCustomizer(TestWithMetaImport.class,
+				Collections.emptyList());
 		assertThat(customizer).isNotNull();
 	}
 
 	@Test
 	void contextCustomizerEqualsAndHashCode() {
-		ContextCustomizer customizer1 = this.factory.createContextCustomizer(TestWithImport.class, null);
-		ContextCustomizer customizer2 = this.factory.createContextCustomizer(TestWithImport.class, null);
-		ContextCustomizer customizer3 = this.factory.createContextCustomizer(TestWithImportAndMetaImport.class, null);
+		ContextCustomizer customizer1 = this.factory.createContextCustomizer(TestWithImport.class,
+				Collections.emptyList());
+		ContextCustomizer customizer2 = this.factory.createContextCustomizer(TestWithImport.class,
+				Collections.emptyList());
+		ContextCustomizer customizer3 = this.factory.createContextCustomizer(TestWithImportAndMetaImport.class,
+				Collections.emptyList());
 		ContextCustomizer customizer4 = this.factory.createContextCustomizer(TestWithSameImportAndMetaImport.class,
-				null);
+				Collections.emptyList());
 		assertThat(customizer1).hasSameHashCodeAs(customizer1);
 		assertThat(customizer1).hasSameHashCodeAs(customizer2);
 		assertThat(customizer1).isEqualTo(customizer1).isEqualTo(customizer2).isNotEqualTo(customizer3);
@@ -78,11 +85,11 @@ class ImportsContextCustomizerFactoryTests {
 	@Test
 	void contextCustomizerEqualsAndHashCodeConsidersComponentScan() {
 		ContextCustomizer customizer1 = this.factory
-			.createContextCustomizer(TestWithImportAndComponentScanOfSomePackage.class, null);
+			.createContextCustomizer(TestWithImportAndComponentScanOfSomePackage.class, Collections.emptyList());
 		ContextCustomizer customizer2 = this.factory
-			.createContextCustomizer(TestWithImportAndComponentScanOfSomePackage.class, null);
+			.createContextCustomizer(TestWithImportAndComponentScanOfSomePackage.class, Collections.emptyList());
 		ContextCustomizer customizer3 = this.factory
-			.createContextCustomizer(TestWithImportAndComponentScanOfAnotherPackage.class, null);
+			.createContextCustomizer(TestWithImportAndComponentScanOfAnotherPackage.class, Collections.emptyList());
 		assertThat(customizer1).isEqualTo(customizer2);
 		assertThat(customizer1).hasSameHashCodeAs(customizer2);
 		assertThat(customizer3).isNotEqualTo(customizer2).isNotEqualTo(customizer1);
@@ -91,15 +98,17 @@ class ImportsContextCustomizerFactoryTests {
 
 	@Test
 	void getContextCustomizerWhenClassHasBeanMethodsShouldThrowException() {
-		assertThatIllegalStateException()
-			.isThrownBy(() -> this.factory.createContextCustomizer(TestWithImportAndBeanMethod.class, null))
+		assertThatIllegalStateException().isThrownBy(
+				() -> this.factory.createContextCustomizer(TestWithImportAndBeanMethod.class, Collections.emptyList()))
 			.withMessageContaining("Test classes cannot include @Bean methods");
 	}
 
 	@Test
 	void contextCustomizerImportsBeans() {
-		ContextCustomizer customizer = this.factory.createContextCustomizer(TestWithImport.class, null);
+		ContextCustomizer customizer = this.factory.createContextCustomizer(TestWithImport.class,
+				Collections.emptyList());
 		AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
+		assertThat(customizer).isNotNull();
 		customizer.customizeContext(context, mock(MergedContextConfiguration.class));
 		context.refresh();
 		assertThat(context.getBean(ImportedBean.class)).isNotNull();
@@ -107,7 +116,8 @@ class ImportsContextCustomizerFactoryTests {
 
 	@Test
 	void selfAnnotatingAnnotationDoesNotCauseStackOverflow() {
-		assertThat(this.factory.createContextCustomizer(TestWithImportAndSelfAnnotatingAnnotation.class, null))
+		assertThat(this.factory.createContextCustomizer(TestWithImportAndSelfAnnotatingAnnotation.class,
+				Collections.emptyList()))
 			.isNotNull();
 	}
 

core/spring-boot-test/src/test/java/org/springframework/boot/test/context/PropertyMappingContextCustomizerFactoryTests.java

@@ -18,6 +18,7 @@ package org.springframework.boot.test.context;
 
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
+import java.util.Collections;
 
 import org.junit.jupiter.api.Test;
 
@@ -28,6 +29,8 @@ import org.springframework.context.annotation.AnnotationConfigApplicationContext
 import org.springframework.context.annotation.Configuration;
 import org.springframework.core.env.ConfigurableEnvironment;
 import org.springframework.test.context.ContextCustomizer;
+import org.springframework.test.context.ContextLoader;
+import org.springframework.test.context.MergedContextConfiguration;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
@@ -46,57 +49,67 @@ class PropertyMappingContextCustomizerFactoryTests {
 
 	@Test
 	void getContextCustomizerWhenHasNoMappingShouldNotAddPropertySource() {
-		ContextCustomizer customizer = this.factory.createContextCustomizer(NoMapping.class, null);
+		ContextCustomizer customizer = this.factory.createContextCustomizer(NoMapping.class, Collections.emptyList());
 		ConfigurableApplicationContext context = mock(ConfigurableApplicationContext.class);
 		ConfigurableEnvironment environment = mock(ConfigurableEnvironment.class);
 		ConfigurableListableBeanFactory beanFactory = mock(ConfigurableListableBeanFactory.class);
 		given(context.getEnvironment()).willReturn(environment);
 		given(context.getBeanFactory()).willReturn(beanFactory);
-		customizer.customizeContext(context, null);
+		customizer.customizeContext(context, getMergedConfigConfiguration());
 		then(environment).shouldHaveNoInteractions();
 	}
 
 	@Test
 	void getContextCustomizerWhenHasTypeMappingShouldReturnCustomizer() {
-		ContextCustomizer customizer = this.factory.createContextCustomizer(TypeMapping.class, null);
+		ContextCustomizer customizer = this.factory.createContextCustomizer(TypeMapping.class, Collections.emptyList());
 		assertThat(customizer).isNotNull();
 	}
 
 	@Test
 	void getContextCustomizerWhenHasAttributeMappingShouldReturnCustomizer() {
-		ContextCustomizer customizer = this.factory.createContextCustomizer(AttributeMapping.class, null);
+		ContextCustomizer customizer = this.factory.createContextCustomizer(AttributeMapping.class,
+				Collections.emptyList());
 		assertThat(customizer).isNotNull();
 	}
 
 	@Test
 	void hashCodeAndEqualsShouldBeBasedOnPropertyValues() {
-		ContextCustomizer customizer1 = this.factory.createContextCustomizer(TypeMapping.class, null);
-		ContextCustomizer customizer2 = this.factory.createContextCustomizer(AttributeMapping.class, null);
-		ContextCustomizer customizer3 = this.factory.createContextCustomizer(OtherMapping.class, null);
+		ContextCustomizer customizer1 = this.factory.createContextCustomizer(TypeMapping.class,
+				Collections.emptyList());
+		ContextCustomizer customizer2 = this.factory.createContextCustomizer(AttributeMapping.class,
+				Collections.emptyList());
+		ContextCustomizer customizer3 = this.factory.createContextCustomizer(OtherMapping.class,
+				Collections.emptyList());
 		assertThat(customizer1).hasSameHashCodeAs(customizer2);
 		assertThat(customizer1).isEqualTo(customizer1).isEqualTo(customizer2).isNotEqualTo(customizer3);
 	}
 
 	@Test
 	void prepareContextShouldAddPropertySource() {
-		ContextCustomizer customizer = this.factory.createContextCustomizer(AttributeMapping.class, null);
+		ContextCustomizer customizer = this.factory.createContextCustomizer(AttributeMapping.class,
+				Collections.emptyList());
 		AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
-		customizer.customizeContext(context, null);
+		customizer.customizeContext(context, getMergedConfigConfiguration());
 		assertThat(context.getEnvironment().getProperty("mapped")).isEqualTo("Mapped");
 	}
 
 	@Test
 	void propertyMappingShouldNotBeUsedWithComponent() {
-		ContextCustomizer customizer = this.factory.createContextCustomizer(AttributeMapping.class, null);
+		ContextCustomizer customizer = this.factory.createContextCustomizer(AttributeMapping.class,
+				Collections.emptyList());
 		AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
 		context.register(ConfigMapping.class);
-		customizer.customizeContext(context, null);
+		customizer.customizeContext(context, getMergedConfigConfiguration());
 		assertThatExceptionOfType(BeanCreationException.class).isThrownBy(context::refresh)
 			.withMessageContaining("The @PropertyMapping annotation "
 					+ "@PropertyMappingContextCustomizerFactoryTests.TypeMappingAnnotation "
 					+ "cannot be used in combination with the @Component annotation @Configuration");
 	}
 
+	private MergedContextConfiguration getMergedConfigConfiguration() {
+		return new MergedContextConfiguration(getClass(), null, null, null, mock(ContextLoader.class));
+	}
+
 	@NoMappingAnnotation
 	static class NoMapping {
 

core/spring-boot-test/src/test/java/org/springframework/boot/test/context/SpringBootContextLoaderAotTests.java

@@ -73,6 +73,7 @@ class SpringBootContextLoaderAotTests {
 			MergedContextConfiguration mergedConfig = testContextBootstrapper.buildMergedContextConfiguration();
 			ApplicationContextInitializer<ConfigurableApplicationContext> contextInitializer = aotContextInitializers
 				.getContextInitializer(testClass);
+			assertThat(contextInitializer).isNotNull();
 			ConfigurableApplicationContext context = (ConfigurableApplicationContext) ((AotContextLoader) mergedConfig
 				.getContextLoader()).loadContextForAotRuntime(mergedConfig, contextInitializer);
 			assertThat(context).isExactlyInstanceOf(GenericApplicationContext.class);

core/spring-boot-test/src/test/java/org/springframework/boot/test/context/SpringBootContextLoaderTests.java

@@ -21,6 +21,7 @@ import java.util.List;
 import java.util.Map;
 import java.util.stream.Collectors;
 
+import org.jspecify.annotations.Nullable;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Disabled;
 import org.junit.jupiter.api.Test;
@@ -288,6 +289,7 @@ class SpringBootContextLoaderTests {
 		TestContext context = new ExposedTestContextManager(testClass).getExposedTestContext();
 		MergedContextConfiguration config = (MergedContextConfiguration) ReflectionTestUtils.getField(context,
 				"mergedConfig");
+		assertThat(config).isNotNull();
 		return TestPropertySourceUtils.convertInlinedPropertiesToMap(config.getPropertySourceProperties());
 	}
 
@@ -494,12 +496,12 @@ class SpringBootContextLoaderTests {
 	private static final class ContextLoaderApplicationContextFailureProcessor
 			implements ApplicationContextFailureProcessor {
 
-		static ApplicationContext failedContext;
+		static @Nullable ApplicationContext failedContext;
 
-		static Throwable contextLoadException;
+		static @Nullable Throwable contextLoadException;
 
 		@Override
-		public void processLoadFailure(ApplicationContext context, Throwable exception) {
+		public void processLoadFailure(ApplicationContext context, @Nullable Throwable exception) {
 			failedContext = context;
 			contextLoadException = exception;
 		}

core/spring-boot-test/src/test/java/org/springframework/boot/test/context/SpringBootTestCustomConfigNameTests.java

@@ -16,6 +16,7 @@
 
 package org.springframework.boot.test.context;
 
+import org.jspecify.annotations.Nullable;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.beans.factory.annotation.Value;
@@ -33,7 +34,7 @@ import static org.assertj.core.api.Assertions.assertThat;
 class SpringBootTestCustomConfigNameTests {
 
 	@Value("${test.foo}")
-	private String foo;
+	private @Nullable String foo;
 
 	@Test
 	void propertyIsLoadedFromConfigFileWithCustomName() {

core/spring-boot-test/src/test/java/org/springframework/boot/test/context/SpringBootTestWithActiveProfilesAndSystemEnvironmentPropertyTests.java

@@ -67,6 +67,7 @@ class SpringBootTestWithActiveProfilesAndSystemEnvironmentPropertyTests {
 			ConfigurableEnvironment environment = new StandardEnvironment();
 			MutablePropertySources sources = environment.getPropertySources();
 			PropertySource<?> source = sources.get(StandardEnvironment.SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME);
+			assertThat(source).isNotNull();
 			Map<String, Object> map = new LinkedHashMap<>((Map<String, Object>) source.getSource());
 			map.put("SPRING_PROFILES_ACTIVE", "local");
 			sources.replace(StandardEnvironment.SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME,

core/spring-boot-test/src/test/java/org/springframework/boot/test/context/SpringBootTestWithTestPropertySourceTests.java

@@ -16,6 +16,7 @@
 
 package org.springframework.boot.test.context;
 
+import org.jspecify.annotations.Nullable;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.beans.factory.annotation.Autowired;
@@ -82,22 +83,22 @@ class SpringBootTestWithTestPropertySourceTests {
 	static class Config {
 
 		@Value("${boot-test-inlined}")
-		private String bootTestInlined;
+		private @Nullable String bootTestInlined;
 
 		@Value("${property-source-inlined}")
-		private String propertySourceInlined;
+		private @Nullable String propertySourceInlined;
 
 		@Value("${property-source-location}")
-		private String propertySourceLocation;
+		private @Nullable String propertySourceLocation;
 
 		@Value("${a}")
-		private String propertySourceInlinedOverridesPropertySourceLocation;
+		private @Nullable String propertySourceInlinedOverridesPropertySourceLocation;
 
 		@Value("${b}")
-		private String bootTestInlinedOverridesPropertySourceLocation;
+		private @Nullable String bootTestInlinedOverridesPropertySourceLocation;
 
 		@Value("${c}")
-		private String propertySourceInlinedOverridesBootTestInlined;
+		private @Nullable String propertySourceInlinedOverridesBootTestInlined;
 
 		@Bean
 		static PropertySourcesPlaceholderConfigurer propertyPlaceholder() {

core/spring-boot-test/src/test/java/org/springframework/boot/test/context/assertj/ApplicationContextAssertProviderTests.java

@@ -43,6 +43,7 @@ import static org.mockito.BDDMockito.then;
 class ApplicationContextAssertProviderTests {
 
 	@Mock
+	@SuppressWarnings("NullAway.Init")
 	private ConfigurableApplicationContext mockContext;
 
 	private RuntimeException startupFailure;
@@ -61,6 +62,7 @@ class ApplicationContextAssertProviderTests {
 	}
 
 	@Test
+	@SuppressWarnings("NullAway") // Test null check
 	void getWhenTypeIsNullShouldThrowException() {
 		assertThatIllegalArgumentException().isThrownBy(
 				() -> ApplicationContextAssertProvider.get(null, ApplicationContext.class, this.mockContextSupplier))
@@ -68,6 +70,7 @@ class ApplicationContextAssertProviderTests {
 	}
 
 	@Test
+	@SuppressWarnings("NullAway") // Test null check
 	void getWhenTypeIsClassShouldThrowException() {
 		assertThatIllegalArgumentException().isThrownBy(
 				() -> ApplicationContextAssertProvider.get(null, ApplicationContext.class, this.mockContextSupplier))
@@ -83,6 +86,7 @@ class ApplicationContextAssertProviderTests {
 	}
 
 	@Test
+	@SuppressWarnings("NullAway") // Test null check
 	void getWhenContextTypeIsClassShouldThrowException() {
 		assertThatIllegalArgumentException()
 			.isThrownBy(() -> ApplicationContextAssertProvider.get(TestAssertProviderApplicationContext.class, null,

core/spring-boot-test/src/test/java/org/springframework/boot/test/context/assertj/ApplicationContextAssertTests.java

@@ -60,6 +60,7 @@ class ApplicationContextAssertTests {
 	}
 
 	@Test
+	@SuppressWarnings("NullAway") // Test null check
 	void createWhenApplicationContextIsNullShouldThrowException() {
 		assertThatIllegalArgumentException().isThrownBy(() -> new ApplicationContextAssert<>(null, null))
 			.withMessageContaining("'applicationContext' must not be null");

core/spring-boot-test/src/test/java/org/springframework/boot/test/context/filter/annotation/FilterAnnotationsTests.java

@@ -80,6 +80,7 @@ class FilterAnnotationsTests {
 
 	private FilterAnnotations get(Class<?> type) {
 		Filters filters = AnnotatedElementUtils.getMergedAnnotation(type, Filters.class);
+		assertThat(filters).isNotNull();
 		return new FilterAnnotations(getClass().getClassLoader(), filters.value());
 	}
 

core/spring-boot-test/src/test/java/org/springframework/boot/test/context/filter/annotation/TypeExcludeFiltersContextCustomizerFactoryTests.java

@@ -16,6 +16,9 @@
 
 package org.springframework.boot.test.context.filter.annotation;
 
+import java.util.Collections;
+
+import org.jspecify.annotations.Nullable;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.boot.context.TypeExcludeFilter;
@@ -46,35 +49,42 @@ class TypeExcludeFiltersContextCustomizerFactoryTests {
 
 	@Test
 	void getContextCustomizerWhenHasNoAnnotationShouldReturnNull() {
-		ContextCustomizer customizer = this.factory.createContextCustomizer(NoAnnotation.class, null);
+		ContextCustomizer customizer = this.factory.createContextCustomizer(NoAnnotation.class,
+				Collections.emptyList());
 		assertThat(customizer).isNull();
 	}
 
 	@Test
 	void getContextCustomizerWhenHasAnnotationShouldReturnCustomizer() {
-		ContextCustomizer customizer = this.factory.createContextCustomizer(WithExcludeFilters.class, null);
+		ContextCustomizer customizer = this.factory.createContextCustomizer(WithExcludeFilters.class,
+				Collections.emptyList());
 		assertThat(customizer).isNotNull();
 	}
 
 	@Test
 	void getContextCustomizerWhenEnclosingClassHasAnnotationShouldReturnCustomizer() {
 		ContextCustomizer customizer = this.factory.createContextCustomizer(WithEnclosingClassExcludeFilters.class,
-				null);
+				Collections.emptyList());
 		assertThat(customizer).isNotNull();
 	}
 
 	@Test
 	void hashCodeAndEquals() {
-		ContextCustomizer customizer1 = this.factory.createContextCustomizer(WithExcludeFilters.class, null);
-		ContextCustomizer customizer2 = this.factory.createContextCustomizer(WithSameExcludeFilters.class, null);
-		ContextCustomizer customizer3 = this.factory.createContextCustomizer(WithDifferentExcludeFilters.class, null);
+		ContextCustomizer customizer1 = this.factory.createContextCustomizer(WithExcludeFilters.class,
+				Collections.emptyList());
+		ContextCustomizer customizer2 = this.factory.createContextCustomizer(WithSameExcludeFilters.class,
+				Collections.emptyList());
+		ContextCustomizer customizer3 = this.factory.createContextCustomizer(WithDifferentExcludeFilters.class,
+				Collections.emptyList());
 		assertThat(customizer1).hasSameHashCodeAs(customizer2);
 		assertThat(customizer1).isEqualTo(customizer1).isEqualTo(customizer2).isNotEqualTo(customizer3);
 	}
 
 	@Test
 	void getContextCustomizerShouldAddExcludeFilters() throws Exception {
-		ContextCustomizer customizer = this.factory.createContextCustomizer(WithExcludeFilters.class, null);
+		ContextCustomizer customizer = this.factory.createContextCustomizer(WithExcludeFilters.class,
+				Collections.emptyList());
+		assertThat(customizer).isNotNull();
 		customizer.customizeContext(this.context, this.mergedContextConfiguration);
 		this.context.refresh();
 		TypeExcludeFilter filter = this.context.getBean(TypeExcludeFilter.class);
@@ -123,8 +133,8 @@ class TypeExcludeFiltersContextCustomizerFactoryTests {
 		}
 
 		@Override
-		public boolean equals(Object obj) {
-			return obj.getClass() == getClass();
+		public boolean equals(@Nullable Object obj) {
+			return obj != null && obj.getClass() == getClass();
 		}
 
 		@Override

core/spring-boot-test/src/test/java/org/springframework/boot/test/context/runner/ContextConsumerTests.java

@@ -66,6 +66,7 @@ class ContextConsumerTests {
 	}
 
 	@Test
+	@SuppressWarnings("NullAway") // Test null check
 	void andThenWithNull() {
 		ContextConsumer<?> consumer = (context) -> {
 		};

core/spring-boot-test/src/test/java/org/springframework/boot/test/http/server/BaseUrlTests.java

@@ -62,6 +62,7 @@ class BaseUrlTests {
 	}
 
 	@Test
+	@SuppressWarnings("NullAway") // Test null check
 	void ofWhenUrlIssNull() {
 		assertThatIllegalArgumentException().isThrownBy(() -> BaseUrl.of(null)).withMessage("'url' must not be null");
 	}
@@ -77,6 +78,7 @@ class BaseUrlTests {
 	}
 
 	@Test
+	@SuppressWarnings("NullAway") // Test null check
 	void ofWhenResolverIsNull() {
 		assertThatIllegalArgumentException().isThrownBy(() -> BaseUrl.of(true, null))
 			.withMessage("'resolver' must not be null");

core/spring-boot-test/src/test/java/org/springframework/boot/test/json/AbstractJsonMarshalTesterTests.java

@@ -29,6 +29,7 @@ import java.util.List;
 import java.util.Map;
 
 import org.assertj.core.api.InstanceOfAssertFactories;
+import org.jspecify.annotations.Nullable;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.io.TempDir;
 
@@ -90,6 +91,7 @@ abstract class AbstractJsonMarshalTesterTests {
 	}
 
 	@Test
+	@SuppressWarnings("NullAway") // Test null check
 	void createWhenResourceLoadClassIsNullShouldThrowException() {
 		assertThatIllegalArgumentException()
 			.isThrownBy(() -> createTester(null, ResolvableType.forClass(ExampleObject.class)))
@@ -97,6 +99,7 @@ abstract class AbstractJsonMarshalTesterTests {
 	}
 
 	@Test
+	@SuppressWarnings("NullAway") // Test null check
 	void createWhenTypeIsNullShouldThrowException() {
 		assertThatIllegalArgumentException().isThrownBy(() -> createTester(getClass(), null))
 			.withMessageContaining("'type' must not be null");
@@ -188,14 +191,15 @@ abstract class AbstractJsonMarshalTesterTests {
 	 */
 	static class ResolvableTypes {
 
-		public List<ExampleObject> listOfExampleObject;
+		public @Nullable List<ExampleObject> listOfExampleObject;
 
-		public ExampleObject[] arrayOfExampleObject;
+		public ExampleObject @Nullable [] arrayOfExampleObject;
 
-		public Map<String, ExampleObject> mapOfExampleObject;
+		public @Nullable Map<String, ExampleObject> mapOfExampleObject;
 
 		static ResolvableType get(String name) {
 			Field field = ReflectionUtils.findField(ResolvableTypes.class, name);
+			assertThat(field).isNotNull();
 			return ResolvableType.forField(field);
 		}
 

core/spring-boot-test/src/test/java/org/springframework/boot/test/json/BasicJsonTesterTests.java

@@ -43,6 +43,7 @@ class BasicJsonTesterTests {
 	private final BasicJsonTester json = new BasicJsonTester(getClass());
 
 	@Test
+	@SuppressWarnings("NullAway") // Test null check
 	void createWhenResourceLoadClassIsNullShouldThrowException() {
 		assertThatIllegalArgumentException().isThrownBy(() -> new BasicJsonTester(null))
 			.withMessageContaining("'resourceLoadClass' must not be null");

core/spring-boot-test/src/test/java/org/springframework/boot/test/json/DuplicateJsonObjectContextCustomizerFactoryTests.java

@@ -43,6 +43,7 @@ class DuplicateJsonObjectContextCustomizerFactoryTests {
 	}
 
 	@Test
+	@SuppressWarnings("NullAway") // Uses null for quick test setup
 	void warningForMultipleVersions() {
 		new DuplicateJsonObjectContextCustomizerFactory().createContextCustomizer(null, null)
 			.customizeContext(null, null);

core/spring-boot-test/src/test/java/org/springframework/boot/test/json/ExampleObject.java

@@ -16,6 +16,8 @@
 
 package org.springframework.boot.test.json;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.util.ObjectUtils;
 
 /**
@@ -23,15 +25,15 @@ import org.springframework.util.ObjectUtils;
  */
 public class ExampleObject {
 
-	private String name;
+	private @Nullable String name;
 
 	private int age;
 
-	public String getName() {
+	public @Nullable String getName() {
 		return this.name;
 	}
 
-	public void setName(String name) {
+	public void setName(@Nullable String name) {
 		this.name = name;
 	}
 

core/spring-boot-test/src/test/java/org/springframework/boot/test/json/ExampleObjectWithView.java

@@ -17,6 +17,7 @@
 package org.springframework.boot.test.json;
 
 import com.fasterxml.jackson.annotation.JsonView;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.util.ObjectUtils;
 
@@ -28,15 +29,15 @@ import org.springframework.util.ObjectUtils;
 public class ExampleObjectWithView {
 
 	@JsonView(TestView.class)
-	private String name;
+	private @Nullable String name;
 
 	private int age;
 
-	public String getName() {
+	public @Nullable String getName() {
 		return this.name;
 	}
 
-	public void setName(String name) {
+	public void setName(@Nullable String name) {
 		this.name = name;
 	}
 

core/spring-boot-test/src/test/java/org/springframework/boot/test/json/GsonTesterIntegrationTests.java

@@ -35,12 +35,16 @@ import static org.assertj.core.api.Assertions.assertThat;
  */
 class GsonTesterIntegrationTests {
 
+	@SuppressWarnings("NullAway.Init")
 	private GsonTester<ExampleObject> simpleJson;
 
+	@SuppressWarnings("NullAway.Init")
 	private GsonTester<List<ExampleObject>> listJson;
 
+	@SuppressWarnings("NullAway.Init")
 	private GsonTester<Map<String, Integer>> mapJson;
 
+	@SuppressWarnings("NullAway.Init")
 	private GsonTester<String> stringJson;
 
 	private Gson gson;

core/spring-boot-test/src/test/java/org/springframework/boot/test/json/GsonTesterTests.java

@@ -20,6 +20,7 @@ import java.util.List;
 
 import com.google.gson.Gson;
 import com.google.gson.GsonBuilder;
+import org.jspecify.annotations.Nullable;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.core.ResolvableType;
@@ -35,12 +36,14 @@ import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException
 class GsonTesterTests extends AbstractJsonMarshalTesterTests {
 
 	@Test
+	@SuppressWarnings("NullAway") // Test null check
 	void initFieldsWhenTestIsNullShouldThrowException() {
 		assertThatIllegalArgumentException().isThrownBy(() -> GsonTester.initFields(null, new GsonBuilder().create()))
 			.withMessageContaining("'testInstance' must not be null");
 	}
 
 	@Test
+	@SuppressWarnings("NullAway") // Test null check
 	void initFieldsWhenMarshallerIsNullShouldThrowException() {
 		assertThatIllegalArgumentException()
 			.isThrownBy(() -> GsonTester.initFields(new InitFieldsTestClass(), (Gson) null))
@@ -55,8 +58,10 @@ class GsonTesterTests extends AbstractJsonMarshalTesterTests {
 		GsonTester.initFields(test, new GsonBuilder().create());
 		assertThat(test.test).isNotNull();
 		assertThat(test.base).isNotNull();
-		assertThat(test.test.getType().resolve()).isEqualTo(List.class);
-		assertThat(test.test.getType().resolveGeneric()).isEqualTo(ExampleObject.class);
+		ResolvableType type = test.test.getType();
+		assertThat(type).isNotNull();
+		assertThat(type.resolve()).isEqualTo(List.class);
+		assertThat(type.resolveGeneric()).isEqualTo(ExampleObject.class);
 	}
 
 	@Override
@@ -66,7 +71,7 @@ class GsonTesterTests extends AbstractJsonMarshalTesterTests {
 
 	abstract static class InitFieldsBaseClass {
 
-		public GsonTester<ExampleObject> base;
+		public @Nullable GsonTester<ExampleObject> base;
 
 		public GsonTester<ExampleObject> baseSet = new GsonTester<>(InitFieldsBaseClass.class,
 				ResolvableType.forClass(ExampleObject.class), new GsonBuilder().create());
@@ -75,7 +80,7 @@ class GsonTesterTests extends AbstractJsonMarshalTesterTests {
 
 	static class InitFieldsTestClass extends InitFieldsBaseClass {
 
-		public GsonTester<List<ExampleObject>> test;
+		public @Nullable GsonTester<List<ExampleObject>> test;
 
 		public GsonTester<ExampleObject> testSet = new GsonTester<>(InitFieldsBaseClass.class,
 				ResolvableType.forClass(ExampleObject.class), new GsonBuilder().create());

core/spring-boot-test/src/test/java/org/springframework/boot/test/json/JacksonTesterIntegrationTests.java

@@ -40,14 +40,19 @@ import static org.assertj.core.api.Assertions.assertThat;
  */
 class JacksonTesterIntegrationTests {
 
+	@SuppressWarnings("NullAway.Init")
 	private JacksonTester<ExampleObject> simpleJson;
 
+	@SuppressWarnings("NullAway.Init")
 	private JacksonTester<ExampleObjectWithView> jsonWithView;
 
+	@SuppressWarnings("NullAway.Init")
 	private JacksonTester<List<ExampleObject>> listJson;
 
+	@SuppressWarnings("NullAway.Init")
 	private JacksonTester<Map<String, Integer>> mapJson;
 
+	@SuppressWarnings("NullAway.Init")
 	private JacksonTester<String> stringJson;
 
 	private static final String JSON = "{\"name\":\"Spring\",\"age\":123}";
@@ -55,8 +60,7 @@ class JacksonTesterIntegrationTests {
 	@Test
 	void typicalTest() throws Exception {
 		JacksonTester.initFields(this, new JsonMapper());
-		String example = JSON;
-		assertThat(this.simpleJson.parse(example).getObject().getName()).isEqualTo("Spring");
+		assertThat(this.simpleJson.parse(JSON).getObject().getName()).isEqualTo("Spring");
 	}
 
 	@Test

core/spring-boot-test/src/test/java/org/springframework/boot/test/json/JacksonTesterTests.java

@@ -18,6 +18,7 @@ package org.springframework.boot.test.json;
 
 import java.util.List;
 
+import org.jspecify.annotations.Nullable;
 import org.junit.jupiter.api.Test;
 import tools.jackson.databind.json.JsonMapper;
 
@@ -34,12 +35,14 @@ import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException
 class JacksonTesterTests extends AbstractJsonMarshalTesterTests {
 
 	@Test
+	@SuppressWarnings("NullAway") // Test null check
 	void initFieldsWhenTestIsNullShouldThrowException() {
 		assertThatIllegalArgumentException().isThrownBy(() -> JacksonTester.initFields(null, new JsonMapper()))
 			.withMessageContaining("'testInstance' must not be null");
 	}
 
 	@Test
+	@SuppressWarnings("NullAway") // Test null check
 	void initFieldsWhenMarshallerIsNullShouldThrowException() {
 		assertThatIllegalArgumentException()
 			.isThrownBy(() -> JacksonTester.initFields(new InitFieldsTestClass(), (JsonMapper) null))
@@ -54,8 +57,10 @@ class JacksonTesterTests extends AbstractJsonMarshalTesterTests {
 		JacksonTester.initFields(test, new JsonMapper());
 		assertThat(test.test).isNotNull();
 		assertThat(test.base).isNotNull();
-		assertThat(test.test.getType().resolve()).isEqualTo(List.class);
-		assertThat(test.test.getType().resolveGeneric()).isEqualTo(ExampleObject.class);
+		ResolvableType type = test.test.getType();
+		assertThat(type).isNotNull();
+		assertThat(type.resolve()).isEqualTo(List.class);
+		assertThat(type.resolveGeneric()).isEqualTo(ExampleObject.class);
 	}
 
 	@Override
@@ -65,7 +70,7 @@ class JacksonTesterTests extends AbstractJsonMarshalTesterTests {
 
 	abstract static class InitFieldsBaseClass {
 
-		public JacksonTester<ExampleObject> base;
+		public @Nullable JacksonTester<ExampleObject> base;
 
 		public JacksonTester<ExampleObject> baseSet = new JacksonTester<>(InitFieldsBaseClass.class,
 				ResolvableType.forClass(ExampleObject.class), new JsonMapper());
@@ -74,7 +79,7 @@ class JacksonTesterTests extends AbstractJsonMarshalTesterTests {
 
 	static class InitFieldsTestClass extends InitFieldsBaseClass {
 
-		public JacksonTester<List<ExampleObject>> test;
+		public @Nullable JacksonTester<List<ExampleObject>> test;
 
 		public JacksonTester<ExampleObject> testSet = new JacksonTester<>(InitFieldsBaseClass.class,
 				ResolvableType.forClass(ExampleObject.class), new JsonMapper());

core/spring-boot-test/src/test/java/org/springframework/boot/test/json/JsonContentAssertTests.java

@@ -23,6 +23,7 @@ import java.io.InputStream;
 import java.nio.file.Path;
 
 import org.assertj.core.api.AssertProvider;
+import org.jspecify.annotations.Nullable;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.io.TempDir;
@@ -63,6 +64,7 @@ class JsonContentAssertTests {
 	private static final JSONComparator COMPARATOR = new DefaultComparator(JSONCompareMode.LENIENT);
 
 	@TempDir
+	@SuppressWarnings("NullAway.Init")
 	public Path tempDir;
 
 	private File temp;
@@ -1288,7 +1290,7 @@ class JsonContentAssertTests {
 
 	}
 
-	private AssertProvider<JsonContentAssert> forJson(String json) {
+	private AssertProvider<JsonContentAssert> forJson(@Nullable String json) {
 		return () -> new JsonContentAssert(JsonContentAssertTests.class, json);
 	}
 

core/spring-boot-test/src/test/java/org/springframework/boot/test/json/JsonContentTests.java

@@ -36,6 +36,7 @@ class JsonContentTests {
 	private static final ResolvableType TYPE = ResolvableType.forClass(ExampleObject.class);
 
 	@Test
+	@SuppressWarnings("NullAway") // Test null check
 	void createWhenResourceLoadClassIsNullShouldThrowException() {
 		assertThatIllegalArgumentException()
 			.isThrownBy(() -> new JsonContent<ExampleObject>(null, TYPE, JSON, Configuration.defaultConfiguration()))
@@ -43,6 +44,7 @@ class JsonContentTests {
 	}
 
 	@Test
+	@SuppressWarnings("NullAway") // Test null check
 	void createWhenJsonIsNullShouldThrowException() {
 		assertThatIllegalArgumentException()
 			.isThrownBy(
@@ -51,6 +53,7 @@ class JsonContentTests {
 	}
 
 	@Test
+	@SuppressWarnings("NullAway") // Test null check
 	void createWhenConfigurationIsNullShouldThrowException() {
 		assertThatIllegalArgumentException()
 			.isThrownBy(() -> new JsonContent<ExampleObject>(getClass(), TYPE, JSON, null))

core/spring-boot-test/src/test/java/org/springframework/boot/test/json/JsonbTesterTests.java

@@ -20,6 +20,7 @@ import java.util.List;
 
 import jakarta.json.bind.Jsonb;
 import jakarta.json.bind.JsonbBuilder;
+import org.jspecify.annotations.Nullable;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.core.ResolvableType;
@@ -35,12 +36,14 @@ import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException
 class JsonbTesterTests extends AbstractJsonMarshalTesterTests {
 
 	@Test
+	@SuppressWarnings("NullAway") // Test null check
 	void initFieldsWhenTestIsNullShouldThrowException() {
 		assertThatIllegalArgumentException().isThrownBy(() -> JsonbTester.initFields(null, JsonbBuilder.create()))
 			.withMessageContaining("'testInstance' must not be null");
 	}
 
 	@Test
+	@SuppressWarnings("NullAway") // Test null check
 	void initFieldsWhenMarshallerIsNullShouldThrowException() {
 		assertThatIllegalArgumentException()
 			.isThrownBy(() -> JsonbTester.initFields(new InitFieldsTestClass(), (Jsonb) null))
@@ -55,8 +58,10 @@ class JsonbTesterTests extends AbstractJsonMarshalTesterTests {
 		JsonbTester.initFields(test, JsonbBuilder.create());
 		assertThat(test.test).isNotNull();
 		assertThat(test.base).isNotNull();
-		assertThat(test.test.getType().resolve()).isEqualTo(List.class);
-		assertThat(test.test.getType().resolveGeneric()).isEqualTo(ExampleObject.class);
+		ResolvableType type = test.test.getType();
+		assertThat(type).isNotNull();
+		assertThat(type.resolve()).isEqualTo(List.class);
+		assertThat(type.resolveGeneric()).isEqualTo(ExampleObject.class);
 	}
 
 	@Override
@@ -66,7 +71,7 @@ class JsonbTesterTests extends AbstractJsonMarshalTesterTests {
 
 	abstract static class InitFieldsBaseClass {
 
-		public JsonbTester<ExampleObject> base;
+		public @Nullable JsonbTester<ExampleObject> base;
 
 		public JsonbTester<ExampleObject> baseSet = new JsonbTester<>(InitFieldsBaseClass.class,
 				ResolvableType.forClass(ExampleObject.class), JsonbBuilder.create());
@@ -75,7 +80,7 @@ class JsonbTesterTests extends AbstractJsonMarshalTesterTests {
 
 	static class InitFieldsTestClass extends InitFieldsBaseClass {
 
-		public JsonbTester<List<ExampleObject>> test;
+		public @Nullable JsonbTester<List<ExampleObject>> test;
 
 		public JsonbTester<ExampleObject> testSet = new JsonbTester<>(InitFieldsBaseClass.class,
 				ResolvableType.forClass(ExampleObject.class), JsonbBuilder.create());

core/spring-boot-test/src/test/java/org/springframework/boot/test/json/ObjectContentTests.java

@@ -35,6 +35,7 @@ class ObjectContentTests {
 	private static final ResolvableType TYPE = ResolvableType.forClass(ExampleObject.class);
 
 	@Test
+	@SuppressWarnings("NullAway") // Test null check
 	void createWhenObjectIsNullShouldThrowException() {
 		assertThatIllegalArgumentException().isThrownBy(() -> new ObjectContent<ExampleObject>(TYPE, null))
 			.withMessageContaining("'object' must not be null");

core/spring-boot-test/src/test/java/org/springframework/boot/test/mock/web/SpringBootMockServletContextTests.java

@@ -47,6 +47,7 @@ import static org.assertj.core.api.Assertions.assertThat;
 @WebAppConfiguration("src/test/webapp")
 class SpringBootMockServletContextTests implements ServletContextAware {
 
+	@SuppressWarnings("NullAway.Init")
 	private ServletContext servletContext;
 
 	@Override

core/spring-boot-test/src/test/java/org/springframework/boot/test/util/TestPropertyValuesTests.java

@@ -21,6 +21,7 @@ import java.util.LinkedHashMap;
 import java.util.Map;
 import java.util.stream.Stream;
 
+import org.jspecify.annotations.Nullable;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.boot.test.util.TestPropertyValues.Pair;
@@ -191,8 +192,10 @@ class TestPropertyValuesTests {
 
 	@Test
 	void pairOfCreatesPair() {
-		Map<String, Object> map = new LinkedHashMap<>();
-		Pair.of("spring", "boot").addTo(map);
+		Map<String, @Nullable Object> map = new LinkedHashMap<>();
+		Pair pair = Pair.of("spring", "boot");
+		assertThat(pair).isNotNull();
+		pair.addTo(map);
 		assertThat(map).containsOnly(entry("spring", "boot"));
 	}
 
@@ -203,8 +206,10 @@ class TestPropertyValuesTests {
 
 	@Test
 	void pairFromMapEntryCreatesPair() {
-		Map<String, Object> map = new LinkedHashMap<>();
-		Pair.fromMapEntry(entry("spring", "boot")).addTo(map);
+		Map<String, @Nullable Object> map = new LinkedHashMap<>();
+		Pair pair = Pair.fromMapEntry(entry("spring", "boot"));
+		assertThat(pair).isNotNull();
+		pair.addTo(map);
 		assertThat(map).containsOnly(entry("spring", "boot"));
 	}
 

core/spring-boot-test/src/test/java/org/springframework/boot/test/web/server/LocalManagementPortTests.java

@@ -16,6 +16,7 @@
 
 package org.springframework.boot.test.web.server;
 
+import org.jspecify.annotations.Nullable;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
 
@@ -36,10 +37,10 @@ import static org.assertj.core.api.Assertions.assertThat;
 class LocalManagementPortTests {
 
 	@Value("${local.management.port}")
-	private String fromValue;
+	private @Nullable String fromValue;
 
 	@LocalManagementPort
-	private String fromAnnotation;
+	private @Nullable String fromAnnotation;
 
 	@Test
 	void testLocalManagementPortAnnotation() {

core/spring-boot-test/src/test/java/org/springframework/boot/test/web/server/LocalServerPortTests.java

@@ -16,6 +16,7 @@
 
 package org.springframework.boot.test.web.server;
 
+import org.jspecify.annotations.Nullable;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
 
@@ -37,10 +38,10 @@ import static org.assertj.core.api.Assertions.assertThat;
 class LocalServerPortTests {
 
 	@Value("${local.server.port}")
-	private String fromValue;
+	private @Nullable String fromValue;
 
 	@LocalServerPort
-	private String fromAnnotation;
+	private @Nullable String fromAnnotation;
 
 	@Test
 	void testLocalServerPortAnnotation() {