spring-mockito

Significantly simplifies Spring bean mocking by providing MockitoPropagatingFactoryPostProcessor that replace original beans with their mocks, therefore, as a result, Autowiring is working fine out of the box.

Simple step by step tutorial

Let's assume that we have two beans:

• errorHandler with method onError() which re-throws corresponding exception,
• integerConverter with method convert() which is returns either an integer value parsed from passed string or it calls autowired instance of errorHandler in case of error.

Here is a simple implementation of those beans:

    public class ErrorHandler{
        public void onError(Throwable e) throws RuntimeException {
            throw new RuntimeException("Exception was generated upon request", e);
        }
    }

    public class IntegerConverter{
        @Autowired
        private ErrorHandler errorHandler;

        public int convert(String value){
            try {
                return Integer.parseInt(value);
            }catch (NumberFormatException e) {
                errorHandler.onError(e);
                return -1;
            }
        }
    }

and corresponding beans.xml:

    <?xml version="1.0" encoding="UTF-8"?>
    <beans xmlns="http://www.springframework.org/schema/beans"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
    
        <bean id="errorHandler" class="org.test.ErrorHandler" />
        <bean id="integerConverter" class="org.test.IntegerConverter" />
    </beans>

Let's create a test to ensure that errorHandler will be called by integerConverter exactly one time in case of error. So, in Mockito's terms:

we need to inject the mocked errorHandler and verify interactions count.

This might be done by adding MockitoPropagatingFactoryPostProcessor as follows:

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes = AutowiredMockTest.MockedConfig.class)
@DirtiesContext(classMode = DirtiesContext.ClassMode.AFTER_EACH_TEST_METHOD)
public class AutowiredMockTest {

    public static class ErrorHandler{
        public void onError(Throwable e) throws RuntimeException {
            throw new RuntimeException("Exception was generated upon request", e);
        }
    }

    public static class IntegerConverter{
        @Autowired
        private ErrorHandler errorHandler;

        public int convert(String value){
            try {
                return Integer.parseInt(value);
            }catch (NumberFormatException e) {
                errorHandler.onError(e);
                return -1;
            }
        }
    }

    @Configuration
    @ImportResource("classpath:/beans.xml")
    static class MockedConfig{
        @Mock
        private ErrorHandler errorHandler;

        @Bean
        public ErrorHandler exceptionGenerator(){
            return errorHandler;
        }

        @Bean
        public MockitoPropagatingFactoryPostProcessor postProcessor(){
            return new MockitoPropagatingFactoryPostProcessor(this);
        }
    }

    @Autowired
    private ErrorHandler errorHandler;

    @Autowired
    private IntegerConverter integerConverter;

    @Test
    public void shouldCallErrorHandlerExactlyOnce() throws Exception {
        // check that Spring was configured properly
        assertNotNull("Spring doesn't properly configured", integerConverter);
        assertNotNull("Spring doesn't properly configured", errorHandler);

        integerConverter.convert("xYz");

        verify(errorHandler, Mockito.times(1)).onError(any(Throwable.class));
        Mockito.verifyNoMoreInteractions(errorHandler);
    }
}