public async Task GetByIdAsync_Success() { List <VehicleModel> vehicleModelList = new List <VehicleModel> { new VehicleModel { Id = 2, MakeId = 1, Name = "X2", Abrv = "x2" }, new VehicleModel { Id = 3, MakeId = 2, Name = "X1", Abrv = "x1" } }; modelRepository.Setup(x => x.GetByIdAsync(It.IsAny <int>())) .ReturnsAsync((int id) => vehicleModelList.Where(v => v.Id == id).Single()); var vehicleModelService = new VehicleModelService(modelRepository.Object); var result = await vehicleModelService.GetByIdAsync(2); result.ShouldBeEquivalentTo(vehicleModelList.First()); }