EndpointTest.java

@RunWith(JukitoRunner.class)
public class EndpointTest {
    public static class Module extends JukitoModule {
        @Override
        protected void configureTest() {
            install(new FactoryModuleBuilder().build(ResponseFactory.class));
        }
    }

    private final String A_USERNAME = "Bobby";
    private final int USER_ID = 1337;

    @Inject
    private UserInformationService userInformationService;
    @Inject
    private Endpoint endpoint;

    @Test
    public void getUsername_delegatesToUserInformationService() {
        endpoint.getUsername(USER_ID);

        verify(userInformationService).getUsername(USER_ID);
    }

    @Test
    public void getUsername_returnsOkWhenUserIsFound() {
        given(userInformationService.getUsername(USER_ID)).willReturn(A_USERNAME);
        int okResponseCode = javax.ws.rs.core.Response.Status.OK.getStatusCode();

        Response result = endpoint.getUsername(USER_ID);

        assertThat(result.getStatusCode()).isEqualTo(okResponseCode);
    }

    @Test
    public void getUser_returnsNotFoundWhenUserIsNotFound() {
        given(userInformationService.getUsername(USER_ID)).willThrow(NotFoundException.class);
        int notFoundStatusCode = javax.ws.rs.core.Response.Status.NOT_FOUND.getStatusCode();

        Response result = endpoint.getUsername(USER_ID);

        assertThat(result.getStatusCode()).isEqualTo(notFoundStatusCode);
    }
}

NotFoundResponse.java

public class NotFoundResponse implements Response {
    @Override
    public int getStatusCode() {
        return 404;
    }
}

OkResponse.java

public class OkResponse implements Response {
    @Override
    public int getStatusCode() {
        return 200;
    }
}

Response.java

public interface Response {
    int getStatusCode();
}

ResponseFactory.java

public interface ResponseFactory {
    OkResponse createOk(String username);

    NotFoundResponse createNotFound();
}