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`@MockitoBean` and `@MockitoSpyBean`

@MockitoBean and @MockitoSpyBean are used on non-static fields in test classes to override beans in the test’s ApplicationContext with a Mockito mock or spy, respectively. In the latter case, an early instance of the original bean is captured and wrapped by the spy.

By default, the annotated field’s type is used to search for candidate beans to override. If multiple candidates match, @Qualifier can be provided to narrow the candidate to override. Alternatively, a candidate whose bean name matches the name of the field will match.

When using @MockitoBean, a new bean will be created if a corresponding bean does not exist. However, if you would like for the test to fail when a corresponding bean does not exist, you can set the enforceOverride attribute to true – for example, @MockitoBean(enforceOverride = true).

To use a by-name override rather than a by-type override, specify the name attribute of the annotation.

Qualifiers, including the name of the field, are used to determine if a separate ApplicationContext needs to be created. If you are using this feature to mock or spy the same bean in several tests, make sure to name the field consistently to avoid creating unnecessary contexts.

Each annotation also defines Mockito-specific attributes to fine-tune the mocking details.

By default, the @MockitoBean annotation uses the REPLACE_OR_CREATE strategy for test bean overriding. If no existing bean matches, a new bean is created on the fly. As mentioned previously, you can switch to the REPLACE strategy by setting the enforceOverride attribute to true.

The @MockitoSpyBean annotation uses the WRAP strategy, and the original instance is wrapped in a Mockito spy. This strategy requires that exactly one candidate bean exists.

Only singleton beans can be overridden. Any attempt to override a non-singleton bean will result in an exception.

When using @MockitoBean to mock a bean created by a FactoryBean, the FactoryBean will be replaced with a singleton mock of the type of object created by the FactoryBean.

When using @MockitoSpyBean to create a spy for a FactoryBean, a spy will be created for the object created by the FactoryBean, not for the FactoryBean itself.

There are no restrictions on the visibility of @MockitoBean and @MockitoSpyBean fields.

Such fields can therefore be public, protected, package-private (default visibility), or private depending on the needs or coding practices of the project.

The following example shows how to use the default behavior of the @MockitoBean annotation:

Java

class OverrideBeanTests {
	@MockitoBean (1)
	CustomService customService;

	// test case body...
}

1	Replace the bean with type `CustomService` with a Mockito `mock`.

In the example above, we are creating a mock for CustomService. If more than one bean of that type exists, the bean named customService is considered. Otherwise, the test will fail, and you will need to provide a qualifier of some sort to identify which of the CustomService beans you want to override. If no such bean exists, a bean definition will be created with an auto-generated bean name.

The following example uses a by-name lookup, rather than a by-type lookup:

Java

class OverrideBeanTests {
	@MockitoBean("service") (1)
	CustomService customService;

	// test case body...

}

1	Replace the bean named `service` with a Mockito `mock`.

If no bean definition named service exists, one is created.

The following example shows how to use the default behavior of the @MockitoSpyBean annotation:

Java

class OverrideBeanTests {
	@MockitoSpyBean (1)
	CustomService customService;

	// test case body...
}

1	Wrap the bean with type `CustomService` with a Mockito `spy`.

In the example above, we are wrapping the bean with type CustomService. If more than one bean of that type exists, the bean named customService is considered. Otherwise, the test will fail, and you will need to provide a qualifier of some sort to identify which of the CustomService beans you want to spy.

The following example uses a by-name lookup, rather than a by-type lookup:

Java

class OverrideBeanTests {
	@MockitoSpyBean("service") (1)
	CustomService customService;

	// test case body...

}

1	Wrap the bean named `service` with a Mockito `spy`.

@MockitoBean and @MockitoSpyBean

`@MockitoBean` and `@MockitoSpyBean`