NoOpCallback implements Callback<Response> { @Override public void failure(RetrofitError error) { }  @Override void success(Response resp, Response response); @Override void failure(RetrofitError error);  }
@Test public void testFailure() { NoOpCallback noOpCallback = new NoOpCallback(); RetrofitError mockRetrofitError = mock(RetrofitError.class); noOpCallback.failure(mockRetrofitError); verifyZeroInteractions(mockRetrofitError); }