`@MockitoBean` cannot be used to directly mock a `FactoryBean`

[duoduobingbing]

Problem

Replacing a bean extending FactoryBean with a @MockitoBean bean does not seem to work. My apologies if I read the docs wrong and this is not supported for @MockitoBean.

Reproducer

The following test succeeds with @MockBean but fails with @MockitoBean

@ExtendWith(SpringExtension.class)
public class BeanFactoryTest {

    @MockitoBean
    private ExampleFactoryBean exampleFactoryBean;

    @Test
    void test(@Autowired ApplicationContext applicationContext) {
        ExampleBean exampleBeanMock = Mockito.mock(ExampleBean.class);
        Mockito.when(exampleBeanMock.testMethod()).thenReturn("somethingElse");
        Mockito.when(this.exampleFactoryBean.getObjectType()).thenReturn((Class)ExampleBean.class);
        Mockito.when(this.exampleFactoryBean.getObject()).thenReturn(exampleBeanMock);

        ExampleBean bean = applicationContext.getBean(ExampleBean.class);
        Assertions.assertEquals("somethingElse", bean.testMethod());
    }

    @Configuration(proxyBeanMethods = false)
    static class TestConfig {
        @Bean
        ExampleFactoryBean exampleFactoryBean() {
            return new ExampleFactoryBean();
        }
    }

    public static class ExampleFactoryBean implements FactoryBean<ExampleBean> {

        @Override
        public ExampleBean getObject() {
            return new ExampleBean() {
                @Override
                public String testMethod() {
                    return "test";
                }
            };
        }

        @Override
        public Class<?> getObjectType() {
            return ExampleBean.class;
        }

        @Override
        public boolean isSingleton() {
            return false;
        }

    }

    public interface ExampleBean {

        String testMethod();

    }

}

The test fails with org.springframework.beans.factory.BeanNotOfRequiredTypeException: Bean named 'exampleFactoryBean' is expected to be of type 'org.example.demo.BeanFactoryTest$ExampleFactoryBean' but was actually of type 'org.springframework.beans.factory.support.NullBean'

Workaround

Replacing @MockitoBean with @MockBean makes the test succeed.

[sbrannen]

Hi @duoduobingbing,

Replacing a bean extending FactoryBean with a @MockitoBean bean does not seem to work. My apologies if I read the docs wrong and this is not supported for @MockitoBean.

With regard to mocking a FactoryBean, there is a TIP in the linked documentation which states the following.

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.

Thus, you should not attempt to mock the FactoryBean directly.

Instead, you should mock the type of bean created by the FactoryBean.

For example, the following modified version of your test class passes.

@ExtendWith(SpringExtension.class)
class MockitoBeanFactoryBeanTests {

	@MockitoBean
	ExampleBean exampleBean;


	@Test
	void test(ApplicationContext context) {
		when(exampleBean.testMethod()).thenReturn("somethingElse");

		ExampleBean bean = context.getBean(ExampleBean.class);
		assertEquals("somethingElse", bean.testMethod());
	}

}

Note that the implementations of ExampleFactoryBean, ExampleBean, and TestConfig have not been changed.

In light of that, I am closing this issue.

Regards,

Sam

[duoduobingbing]

Thank you so much for taking the time to look into this.

I was not quite sure if the tip

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.

only meant that non-singleton beans emitted by the FactoryBean are not supported. Especially because it worked with @MockBean.

So, thanks for clarifying this