public void CreateUser() { string testUser = "******"; string testMessage = String.Format("A user has signed up: {0}", testUser); dynamic userSignup = new ExpandoObject(); userSignup.sendUserCreatedMessage = new Action <string>((user) => { this.isSent = true; Assert.AreEqual(testMessage, user, "the user was not supplied correctly"); }); IRequest request = base.BuildTestRequest().Object; var mockClients = new Mock <IHubCallerConnectionContext <dynamic> >(); mockClients.Setup(m => m.All).Returns((ExpandoObject)userSignup); var mockHubCallerContext = new Mock <HubCallerContext>(request, "1"); ChatHub hub = new ChatHub() { Context = mockHubCallerContext.Object, Clients = mockClients.Object, Groups = mockGroupManager.Object }; hub.CreateUser(testUser); }