Introduce enforceOverride flag in @⁠TestBean and @⁠MockitoBean

Prior to this commit, @⁠MockitoBean could be used to either create or
replace a bean definition, but @⁠TestBean could only be used to replace
a bean definition.

However, Bean Override implementations should require the presence of
an existing bean definition by default (i.e. literally "override" by
default), while giving the user the option to have a new bean
definition created if desired.

To address that, this commit introduces a new `enforceOverride`
attribute in @⁠TestBean and @⁠MockitoBean that defaults to true but
allows the user to decide if it's OK to create a bean for a nonexistent
bean definition.

Closes gh-33613

Author: sbrannen

framework-docs/modules/ROOT/pages/testing/annotations/integration-spring/annotation-mockitobean.adoc

@@ -11,6 +11,10 @@ to override. If multiple candidates match, `@Qualifier` can be provided to narro
 candidate to override. Alternatively, a candidate whose bean definition name matches the
 name of the field will match.
 
+When using `@MockitoBean`, if you would like for a new bean definition to be created when
+a corresponding bean definition does not exist, set the `enforceOverride` attribute to
+`false` – for example, `@MockitoBean(enforceOverride = false)`.
+
 To use a by-name override rather than a by-type override, specify the `name` attribute
 of the annotation.
 

framework-docs/modules/ROOT/pages/testing/annotations/integration-spring/annotation-testbean.adoc

@@ -15,6 +15,10 @@ to override. If multiple candidates match, `@Qualifier` can be provided to narro
 candidate to override. Alternatively, a candidate whose bean definition name matches the
 name of the field will match.
 
+If you would like for a new bean definition to be created when a corresponding bean
+definition does not exist, set the `enforceOverride` attribute to `false` – for example,
+`@TestBean(enforceOverride = false)`.
+
 To use a by-name override rather than a by-type override, specify the `name` attribute
 of the annotation.
 

spring-test/src/main/java/org/springframework/test/context/bean/override/convention/TestBean.java

@@ -37,7 +37,10 @@
  * used to help disambiguate. In the absence of a {@code @Qualifier} annotation,
  * the name of the annotated field will be used as a qualifier. Alternatively,
  * you can explicitly specify a bean name to replace by setting the
- * {@link #value()} or {@link #name()} attribute.
+ * {@link #value() value} or {@link #name() name} attribute. If you would like
+ * for a new bean definition to be created when a corresponding bean definition
+ * does not exist, set the {@link #enforceOverride() enforceOverride} attribute
+ * to {@code false}.
  *
  * <p>The instance is created from a zero-argument static factory method in the
  * test class whose return type is compatible with the annotated field. In the
@@ -143,4 +146,16 @@
 	 */
 	String methodName() default "";
 
+	/**
+	 * Whether to require the existence of a bean definition for the bean being
+	 * overridden.
+	 * <p>Defaults to {@code true} which means that an exception will be thrown
+	 * if a corresponding bean definition does not exist.
+	 * <p>Set to {@code false} to create a new bean definition when a corresponding
+	 * bean definition does not exist.
+	 * @see org.springframework.test.context.bean.override.BeanOverrideStrategy#REPLACE_DEFINITION
+	 * @see org.springframework.test.context.bean.override.BeanOverrideStrategy#REPLACE_OR_CREATE_DEFINITION
+	 */
+	boolean enforceOverride() default true;
+
 }

spring-test/src/main/java/org/springframework/test/context/bean/override/convention/TestBeanOverrideMetadata.java

@@ -33,6 +33,7 @@
  *
  * @author Simon Baslé
  * @author Stephane Nicoll
+ * @author Sam Brannen
  * @since 6.2
  */
 final class TestBeanOverrideMetadata extends OverrideMetadata {
@@ -41,9 +42,9 @@ final class TestBeanOverrideMetadata extends OverrideMetadata {
 
 
 	TestBeanOverrideMetadata(Field field, ResolvableType beanType, @Nullable String beanName,
-			Method overrideMethod) {
+			BeanOverrideStrategy strategy, Method overrideMethod) {
 
-		super(field, beanType, beanName, BeanOverrideStrategy.REPLACE_DEFINITION);
+		super(field, beanType, beanName, strategy);
 		this.overrideMethod = overrideMethod;
 	}
 

spring-test/src/main/java/org/springframework/test/context/bean/override/convention/TestBeanOverrideProcessor.java

@@ -31,11 +31,14 @@
 import org.springframework.core.ResolvableType;
 import org.springframework.test.context.TestContextAnnotationUtils;
 import org.springframework.test.context.bean.override.BeanOverrideProcessor;
+import org.springframework.test.context.bean.override.BeanOverrideStrategy;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.ReflectionUtils;
 import org.springframework.util.ReflectionUtils.MethodFilter;
-import org.springframework.util.StringUtils;
+
+import static org.springframework.test.context.bean.override.BeanOverrideStrategy.REPLACE_DEFINITION;
+import static org.springframework.test.context.bean.override.BeanOverrideStrategy.REPLACE_OR_CREATE_DEFINITION;
 
 /**
  * {@link BeanOverrideProcessor} implementation for {@link TestBean @TestBean}
@@ -52,30 +55,34 @@ class TestBeanOverrideProcessor implements BeanOverrideProcessor {
 
 	@Override
 	public TestBeanOverrideMetadata createMetadata(Annotation overrideAnnotation, Class<?> testClass, Field field) {
-		if (!(overrideAnnotation instanceof TestBean testBeanAnnotation)) {
+		if (!(overrideAnnotation instanceof TestBean testBean)) {
 			throw new IllegalStateException("Invalid annotation passed to %s: expected @TestBean on field %s.%s"
 					.formatted(getClass().getSimpleName(), field.getDeclaringClass().getName(), field.getName()));
 		}
+
+		String beanName = (!testBean.name().isBlank() ? testBean.name() : null);
+		String methodName = testBean.methodName();
+		BeanOverrideStrategy strategy = (testBean.enforceOverride() ? REPLACE_DEFINITION : REPLACE_OR_CREATE_DEFINITION);
+
 		Method overrideMethod;
-		String methodName = testBeanAnnotation.methodName();
 		if (!methodName.isBlank()) {
 			// If the user specified an explicit method name, search for that.
 			overrideMethod = findTestBeanFactoryMethod(testClass, field.getType(), methodName);
 		}
 		else {
-			// Otherwise, search for candidate factory methods the field name
-			// or explicit bean name (if any).
+			// Otherwise, search for candidate factory methods whose names match either
+			// the field name or the explicit bean name (if any).
 			List<String> candidateMethodNames = new ArrayList<>();
 			candidateMethodNames.add(field.getName());
 
-			String beanName = testBeanAnnotation.name();
-			if (StringUtils.hasText(beanName)) {
+			if (beanName != null) {
 				candidateMethodNames.add(beanName);
 			}
 			overrideMethod = findTestBeanFactoryMethod(testClass, field.getType(), candidateMethodNames);
 		}
-		String beanName = (StringUtils.hasText(testBeanAnnotation.name()) ? testBeanAnnotation.name() : null);
-		return new TestBeanOverrideMetadata(field, ResolvableType.forField(field, testClass), beanName, overrideMethod);
+
+		return new TestBeanOverrideMetadata(
+				field, ResolvableType.forField(field, testClass), beanName, strategy, overrideMethod);
 	}
 
 	/**

spring-test/src/main/java/org/springframework/test/context/bean/override/mockito/MockitoBean.java

@@ -33,13 +33,14 @@
  * {@link org.springframework.context.ApplicationContext ApplicationContext}
  * using a Mockito mock.
  *
- * <p>If no explicit {@link #name()} is specified, a target bean definition is
- * selected according to the type of the annotated field, and there must be
- * exactly one such candidate definition in the context. A {@code @Qualifier}
- * annotation can be used to help disambiguate.
- * If a {@link #name()} is specified, either the definition exists in the
- * application context and is replaced, or it doesn't and a new one is added to
- * the context.
+ * <p>If no explicit {@link #name() name} is specified, a target bean definition
+ * is selected according to the type of the annotated field, and there must be
+ * exactly one such candidate definition in the context. Otherwise, a {@code @Qualifier}
+ * annotation can be used to help disambiguate between multiple candidates. If a
+ * {@link #name() name} is specified, by default a corresponding bean definition
+ * must exist in the application context. If you would like for a new bean definition
+ * to be created when a corresponding bean definition does not exist, set the
+ * {@link #enforceOverride() enforceOverride} attribute to {@code false}.
  *
  * <p>Dependencies that are known to the application context but are not beans
  * (such as those
@@ -51,6 +52,7 @@
  * Any attempt to override a non-singleton bean will result in an exception.
  *
  * @author Simon Baslé
+ * @author Sam Brannen
  * @since 6.2
  * @see org.springframework.test.context.bean.override.mockito.MockitoSpyBean @MockitoSpyBean
  * @see org.springframework.test.context.bean.override.convention.TestBean @TestBean
@@ -100,4 +102,16 @@
 	 */
 	MockReset reset() default MockReset.AFTER;
 
+	/**
+	 * Whether to require the existence of a bean definition for the bean being
+	 * overridden.
+	 * <p>Defaults to {@code true} which means that an exception will be thrown
+	 * if a corresponding bean definition does not exist.
+	 * <p>Set to {@code false} to create a new bean definition when a corresponding
+	 * bean definition does not exist.
+	 * @see org.springframework.test.context.bean.override.BeanOverrideStrategy#REPLACE_DEFINITION
+	 * @see org.springframework.test.context.bean.override.BeanOverrideStrategy#REPLACE_OR_CREATE_DEFINITION
+	 */
+	boolean enforceOverride() default true;
+
 }

spring-test/src/main/java/org/springframework/test/context/bean/override/mockito/MockitoBeanOverrideMetadata.java

@@ -37,6 +37,9 @@
 import org.springframework.util.ClassUtils;
 import org.springframework.util.StringUtils;
 
+import static org.springframework.test.context.bean.override.BeanOverrideStrategy.REPLACE_DEFINITION;
+import static org.springframework.test.context.bean.override.BeanOverrideStrategy.REPLACE_OR_CREATE_DEFINITION;
+
 /**
  * {@link OverrideMetadata} implementation for Mockito {@code mock} support.
  *
@@ -54,15 +57,17 @@ class MockitoBeanOverrideMetadata extends AbstractMockitoOverrideMetadata {
 	private final boolean serializable;
 
 
-	MockitoBeanOverrideMetadata(Field field, ResolvableType typeToMock, MockitoBean annotation) {
-		this(field, typeToMock, (StringUtils.hasText(annotation.name()) ? annotation.name() : null),
-				annotation.reset(), annotation.extraInterfaces(), annotation.answers(), annotation.serializable());
+	MockitoBeanOverrideMetadata(Field field, ResolvableType typeToMock, MockitoBean mockitoBean) {
+		this(field, typeToMock, (!mockitoBean.name().isBlank() ? mockitoBean.name() : null),
+			(mockitoBean.enforceOverride() ? REPLACE_DEFINITION : REPLACE_OR_CREATE_DEFINITION),
+			mockitoBean.reset(), mockitoBean.extraInterfaces(), mockitoBean.answers(), mockitoBean.serializable());
 	}
 
-	private MockitoBeanOverrideMetadata(Field field, ResolvableType typeToMock, @Nullable String beanName, MockReset reset,
-			Class<?>[] extraInterfaces, @Nullable Answers answers, boolean serializable) {
+	private MockitoBeanOverrideMetadata(Field field, ResolvableType typeToMock, @Nullable String beanName,
+			BeanOverrideStrategy strategy, MockReset reset, Class<?>[] extraInterfaces, @Nullable Answers answers,
+			boolean serializable) {
 
-		super(field, typeToMock, beanName, BeanOverrideStrategy.REPLACE_OR_CREATE_DEFINITION, reset, false);
+		super(field, typeToMock, beanName, strategy, reset, false);
 		Assert.notNull(typeToMock, "'typeToMock' must not be null");
 		this.extraInterfaces = asClassSet(extraInterfaces);
 		this.answers = (answers != null ? answers : Answers.RETURNS_DEFAULTS);

spring-test/src/test/java/org/springframework/test/context/bean/override/convention/TestBeanForByTypeLookupIntegrationTests.java

@@ -39,6 +39,9 @@
 @SpringJUnitConfig
 public class TestBeanForByTypeLookupIntegrationTests {
 
+	@TestBean(enforceOverride = false)
+	MessageService messageService;
+
 	@TestBean
 	ExampleService anyNameForService;
 
@@ -50,6 +53,11 @@ public class TestBeanForByTypeLookupIntegrationTests {
 	@CustomQualifier
 	StringBuilder anyNameForStringBuilder2;
 
+
+	static MessageService messageService() {
+		return () -> "mocked nonexistent bean definition";
+	}
+
 	static ExampleService anyNameForService() {
 		return new RealExampleService("Mocked greeting");
 	}
@@ -63,6 +71,12 @@ static StringBuilder someString2() {
 	}
 
 
+	@Test
+	void overrideIsFoundByTypeForNonexistentBeanDefinition(ApplicationContext ctx) {
+		assertThat(this.messageService).isSameAs(ctx.getBean(MessageService.class));
+		assertThat(this.messageService.getMessage()).isEqualTo("mocked nonexistent bean definition");
+	}
+
 	@Test
 	void overrideIsFoundByType(ApplicationContext ctx) {
 		assertThat(this.anyNameForService)
@@ -114,4 +128,10 @@ StringBuilder beanString3() {
 		}
 	}
 
+	@FunctionalInterface
+	interface MessageService {
+
+		String getMessage();
+	}
+
 }

spring-test/src/test/java/org/springframework/test/context/bean/override/convention/TestBeanOverrideMetadataTests.java

@@ -24,6 +24,7 @@
 
 import org.springframework.beans.factory.annotation.Qualifier;
 import org.springframework.core.ResolvableType;
+import org.springframework.test.context.bean.override.BeanOverrideStrategy;
 import org.springframework.test.context.bean.override.OverrideMetadata;
 import org.springframework.util.ReflectionUtils;
 import org.springframework.util.StringUtils;
@@ -124,7 +125,8 @@ private Method sampleMethod(String noArgMethodName) {
 	private TestBeanOverrideMetadata createMetadata(Field field, Method overrideMethod) {
 		TestBean annotation = field.getAnnotation(TestBean.class);
 		String beanName = (StringUtils.hasText(annotation.name()) ? annotation.name() : null);
-		return new TestBeanOverrideMetadata(field, ResolvableType.forClass(field.getType()), beanName, overrideMethod);
+		return new TestBeanOverrideMetadata(
+				field, ResolvableType.forClass(field.getType()), beanName, BeanOverrideStrategy.REPLACE_DEFINITION, overrideMethod);
 	}
 
 	static class SampleOneOverride {

spring-test/src/test/java/org/springframework/test/context/bean/override/mockito/MockitoBeanForByNameLookupIntegrationTests.java

@@ -48,10 +48,10 @@ public class MockitoBeanForByNameLookupIntegrationTests {
 	@MockitoBean(name = "nestedField")
 	ExampleService renamed2;
 
-	@MockitoBean(name = "nonExistingBean")
+	@MockitoBean(name = "nonExistingBean", enforceOverride = false)
 	ExampleService nonExisting1;
 
-	@MockitoBean(name = "nestedNonExistingBean")
+	@MockitoBean(name = "nestedNonExistingBean", enforceOverride = false)
 	ExampleService nonExisting2;