測試某種方法，並引發異常

Question

我開始使用TDD（和MoQ）。我有一個方法接受訂單併爲該訂單創建唯一的CustomerId。

public class CustomerService 
    { 

     public CustomerService(IOrderRepository orderRepo) 
     { 
      _orderRepo = orderRepo; 
     } 

     public string Create(Order order) 
     { 
      //1. Save the Order that comes in, irrespective of being valid or not. 
      _orderRepo.Save(order); 

      //2. If the order is invalid, throw an exception. 
      if (!isValid(order)) 
       throw new ArgumentException(); 

      //3. Create a Customer, generate a unique CustomerId and return that. 
      return createCustomerAndGenerateCustomerId(order); 
     } 

    } 

下面的測試似乎並不正確工作：

[Test] 
    [ExpectedException(typeof(ArgumentException))] 
    public void Create_WhenPassedInvalidOrder_StillPersistsIt() 
    { 
     //Arrange 
     var order = new Order(); //This is invalid, as it has some mandatory fields missing 
     var mockOrderRepo = new Mock<IOrderRepository>(); 
     var customerService = new CustomerService(mockOrderRepo.Object); 

     //Act 
     customerService.Create(order); //This should call Save() on the order repo, but still throw an exception. 

     //Assert 
     mockOrderRepo.Verify(o => o.Save(order), Times.Once()); 
    } 

這個測試總是通過，即使我不叫_orderRepo.Save（）。我究竟做錯了什麼？

Answer 1

在這種情況下，您不能使用ExpectedException，因爲Nunit會在測試級別嘗試/捕獲異常，所以您的mockOrderRepo.Verify永遠不會被調用。

所以，你需要手動嘗試抓住你的customerService.Create電話 - 如果你想在拋出的異常手動斷言 - 或者你的Assert.Throws if you're using Nunit 2.5 or higher：

[Test] 
public void Create_WhenPassedInvalidOrder_StillPersistsIt() 
{ 
    //Arrange 
    var order = new Order(); 
    var mockOrderRepo = new Mock<IOrderRepository>(); 
    var customerService = new CustomerService(mockOrderRepo.Object); 

    //Act 
    Assert.Throws<ArgumentException>(() => customerService.Create(order)); 

    //Assert 
    mockOrderRepo.Verify(o => o.Save(order), Times.Once()); 
}