public async void TestSpeakSentence() { var context = new MockContext <IPlayAudio>(); context.Arrange(m => m.PlayAudioAsync("id", The <PlayAudioData> .Is(d => IsValidSpeakSentenceData(d)), null)) .Returns(Task.FromResult(0)); var instance = new PlayAudio(context); await instance.SpeakSentenceAsync("id", "Hello"); }