public async void DeliveryService_AssignCourierToDeliveryAsync_throws_exception_when_delivery_with_specified_id_is_not_exists() { // Arrange var dto = A.New <AssignCourierToDeliveryDtoSave>(); _deliveryRepository.Setup(x => x.GetDeliveryByIdAsync(dto.DeliveryId)).ReturnsAsync(() => null); // Act Func <Task> action = async() => { await _service.AssignCourierToDeliveryAsync(dto); }; // Assert await action.Should().ThrowAsync <KeyNotFoundException>().WithMessage($"Delivery not found with specified Id: {dto.DeliveryId}"); _deliveryRepository.Verify(x => x.GetDeliveryByIdAsync(dto.DeliveryId), Times.Once()); }