public void GetFacebookFriendsTest() { //Arrange var facebook = Mock.Of <IFacebookService>(); var facebookMock = Mock.Get(facebook); facebookMock.Setup(m => m.GetFriends()).Returns("{json of friends}"); var sut = new FriendsController(facebook); //Act var actionResult = sut.GetFacebookFriends(); //Assert //...do your assertions here }