@Test
public void fileSendAcceptedShouldPassThroughUsingExecutor() {

    wrapper.fileSendAccepted(100, "fileName", 98765, 1050);
    final ArgumentCaptor<Runnable> runnableCaptor = ArgumentCaptor.forClass(Runnable.class);
    verifyZeroInteractions(messageResponder);
    verify(executorService).execute(runnableCaptor.capture());
    runnableCaptor.getValue().run();
    verify(messageResponder).fileSendAccepted(100, "fileName", 98765, 1050);
}