public void GetAllAsync_Returns_Enumerable_IVehicleMakeBase() { var list = new Mock <IEnumerable <IVehicleMakeBase> >(); repoMock.Setup(s => s.GetMakerBaseAsync()).Returns(new Task <IEnumerable <IVehicleMakeBase> >(() => list.Object)); uowMock.SetupGet(s => s.Makers).Returns(repoMock.Object); var makeService = new VehicleMakeService(uowMock.Object); var make = makeService.GetAllMakeAsync(); //Assert Assert.IsAssignableFrom <Task <IEnumerable <IVehicleMakeBase> > >(make); }