@SuppressWarnings("ResultOfMethodCallIgnored")
@Test
public void toString_returnFromResult_resultIsMessage() {

    Message result = Mockito.mock(Message.class);
    Mockito.doReturn("STRING FROM RESULT").when(result).toString();
    ResultListenerProxy proxy = new ResultListenerProxy(mSender);
    proxy.onResult(result);
    Mockito.verify(mSender).deliver(mMessageCaptor.capture());
    Message<ResultListener<Object>, Void> message = mMessageCaptor.getValue();
    Assert.assertNotNull(message);
    Assert.assertEquals("STRING FROM RESULT", message.toString());
}