How to capture a list of specific type with mockito

Question

Is there a way to capture a list of specific type using mockitos ArgumentCaptore. This doesn\'t work:

ArgumentCaptor> argumen         


        

Answer 1

There is an open issue in Mockito's GitHub about this exact problem.

I have found a simple workaround that does not force you to use annotations in your tests:

import org.mockito.ArgumentCaptor;
import org.mockito.Captor;
import org.mockito.MockitoAnnotations;

public final class MockitoCaptorExtensions {

    public static  ArgumentCaptor captorFor(final CaptorTypeReference argumentTypeReference) {
        return new CaptorContainer().captor;
    }

    public static  ArgumentCaptor captorFor(final Class argumentClass) {
        return ArgumentCaptor.forClass(argumentClass);
    }

    public interface CaptorTypeReference {

        static  CaptorTypeReference genericType() {
            return new CaptorTypeReference() {
            };
        }

        default T nullOfGenericType() {
            return null;
        }

    }

    private static final class CaptorContainer {

        @Captor
        private ArgumentCaptor captor;

        private CaptorContainer() {
            MockitoAnnotations.initMocks(this);
        }

    }

}

What happens here is that we create a new class with the @Captor annotation and inject the captor into it. Then we just extract the captor and return it from our static method.

In your test you can use it like so:

ArgumentCaptor>>> fancyCaptor = captorFor(genericType());

Or with syntax that resembles Jackson's TypeReference:

ArgumentCaptor>>> fancyCaptor = captorFor(
    new CaptorTypeReference>>>() {
    }
);

It works, because Mockito doesn't actually need any type information (unlike serializers, for example).