Unit testing ContainerRequestFilter which uses ResourceInfo with mockito

Question

I'm trying to use Mockito to unit test a ContainerRequestFilter, which is applied using @NameBinding. The filter checks an annotation field to determine what to do. See sample code:

Annotation

@Target({TYPE, METHOD})
@NameBinding
@Retention(RetentionPolicy.RUNTIME)
public @interface MyAnnotation {
    MyEnum info() default MyEnum.DEFAULT;
}

MyEnum

public enum MyEnum {
    VALUE1,
    VALUE2,
    DEFAULT
}

Annotated Filter which uses MyEnum as conditional

@MyAnnotation
public class MyFilter implements ContainerRequestFilter {

    @Context
    private ResourceInfo resourceInfo;

    @Override
    public void filter(ContainerRequestContext containerRequestContext) throws IOException {

        if (resourceInfo.getResourceMethod().getAnnotation(MyAnnotation.class).info().equals(MyEnum.VALUE1)) 
        {
            // set some value or throw some exception (this can be verified in the test)
        }

        if (resourceInfo.getResourceMethod().getAnnotation(MyAnnotation.class).info().equals(MyEnum.VALUE2))
        {
           // set some value or throw some exception (this can be verified in the test)
        }
    }
}

Annotated Resource methods

@Path("/somepath1")
public class MyResource1
{
    @GET
    @MyAnnotation(info = MyEnum.VALUE1)
    public Response someResourceMethod()
    {
        // return response
    } 
}


@Path("/somepath2")
public class MyResource2
{
    @GET
    @MyAnnotation(info = MyEnum.VALUE2)
    public Response someResourceMethod()
    {
        // return response
    } 
}

This design makes it easy to just add enum values when there are new conditions to be added to the filter.

How can I unit test MyFilter, by varying the values in the conditional?

One approach I tried was to mock ResourceInfo and then return mock Method when resourceInfo.getResourceMethod(), but this cannot be done since Method is a final class.

Also mocking objects you don't own is not recommended, so is there a different approach to test this? I am also not wedded to Mockito, so open to any other suggestions.

Answer 1

The easiest way is to just create a dummy class for the test, and do a little reflection to get the Method on the class

@Test
public void testEnumOne() throws Exception {
   Method methodOne = MockClass.class.getDeclaredMethod("enumOne");
   Mockito.when(resourceInfo.getResourceMethod()).thenReturn(methodOne);
}

private static class MockClass {
    @MyAnnotation(info=MyEnum.VALUE1)
    public void enumOne() {}
    @MyAnnotation(info=MyEnum.VALUE2)
    public void enumTwo() {}
}

Here's a complete test.

@RunWith(MockitoJUnitRunner.class)
public class FilterAnnotationTest {

    @Mock
    private ResourceInfo resourceInfo;

    @Mock
    private ContainerRequestContext context;

    @Spy
    private Service service;

    private MyFilter filter;

    @Before
    public void setUp() {
        filter = new MyFilter(resourceInfo, service);
    }

    @Test
    public void testEnumOne() throws Exception {
       Method methodOne = MockClass.class.getDeclaredMethod("enumOne");
       Mockito.when(resourceInfo.getResourceMethod()).thenReturn(methodOne);

       filter.filter(context);
       Mockito.verify(service).methodOne();
    }

    @Test
    public void testEnumTwo() throws Exception {
        Method methodTwo = MockClass.class.getDeclaredMethod("enumTwo");
        Mockito.when(resourceInfo.getResourceMethod()).thenReturn(methodTwo);

        filter.filter(context);
        Mockito.verify(service).methodTwo();
    }


    private enum MyEnum {
        VALUE1, VALUE2
    }

    @Target({ METHOD })
    @Retention(RUNTIME)
    private @interface MyAnnotation {
         MyEnum info();
    }

    private static class MyFilter implements ContainerRequestFilter {

        private final ResourceInfo resourceInfo;
        private final Service service;

        @Inject
        public MyFilter(ResourceInfo resourceInfo, Service service) {
            this.resourceInfo = resourceInfo;
            this.service = service;
        }

        @Override
        public void filter(ContainerRequestContext containerRequestContext) throws IOException {
            MyAnnotation anno = resourceInfo.getResourceMethod().getAnnotation(MyAnnotation.class);
            if (anno.info() == MyEnum.VALUE1) {
                service.methodOne();
            } else if (anno.info() == MyEnum.VALUE2) {
                service.methodTwo();
            }
        }
    }

    private static class MockClass {
        @MyAnnotation(info=MyEnum.VALUE1)
        public void enumOne() {}
        @MyAnnotation(info=MyEnum.VALUE2)
        public void enumTwo() {}
    }

    public interface Service {
        void methodOne();
        void methodTwo();
    }
}