### Question:
ForwardingServerCallListener extends PartialForwardingServerCallListener<ReqT> { @Override public void onMessage(ReqT message) { delegate().onMessage(message); }  @Override void onMessage(ReqT message);  }### Answer:
@Test public void onMessage() { forwarder.onMessage(12345); verify(serverCallListener).onMessage(12345); }
@Test public void onMessage() { forwarder.onMessage(null); verify(serverCallListener).onMessage(null); }