public async Task OnBroadcast_Send_Message_To_All() { // arrange Mock <IHubCallerClients <IChatClient> > mockClients = new Mock <IHubCallerClients <IChatClient> >(); Mock <IChatClient> mockClientProxy = new Mock <IChatClient>(); mockClients.Setup(clients => clients.All).Returns(mockClientProxy.Object); ChatHub chatHub = new ChatHub() { Clients = mockClients.Object }; // act await chatHub.BroadcastMessage("test works"); // assert mockClients.Verify(clients => clients.All, Times.Once); mockClients.Verify(clients => clients.All.SendMessage(It.Is <string>(x => x.Equals("test works"))), Times.Once); mockClientProxy.Verify( clientProxy => clientProxy.SendMessage( It.Is <string>(x => !string.IsNullOrEmpty(x))), Times.Once); }