單元測試 - 無法從存儲庫類訪問方法

Question

我正在編寫一個單元測試，它驗證使用正確的數據選擇了特定的產品。目前，該測試正在提供以下錯誤：

System.NullReferenceException：未將對象引用設置爲對象的實例。

While debugging through the test, I noticed that my result variable is null... I thought I was calling my SelectProduct method correctly, but not sure what is wrong.

Additional question - Any suggestions on how to better Assert?

[TestClass] 
    public class ProductRepositoryTests 
    { 
     [TestMethod] 
     public void SelectProduct_selectProduct_productIsSelected() 
     {   
      // access ProductRepository 
      Mock<IProductRepository> mock = new Mock<IProductRepository>(); 

      // Arrange - mocked product 
      Product product1 = new Product 
      { 
       ProductId = 1, 
       ProductName = "Snicker Bar", 
       ProductPrice = .25M, 
       ProductCategory = "Candy", 
       ProductQuantity = 12 
      }; 

      // Act - select new product using SelectProduct method 
      var result = mock.Object.SelectProduct(product1.ProductId); 

      // Assert 
      Assert.AreEqual(result.ProductId, 1); 
      Assert.AreEqual(result.ProductName, "Snicker Bar"); 
      Assert.AreEqual(result.ProductPrice, .25M); 
     } 
    } 

這裏是我的庫層中的其他的代碼：

接口：

public interface IProductRepository 
{ 
    Product SelectProduct(int productId); 
} 

repository類：

public class ProductRepository : IProductRepository 
    { 
     public Product SelectProduct(int productId) 
     { 
      throw new System.NotImplementedException(); 
     } 
    } 

Answer 1

你似乎想要測試ProductRepository類，而是測試一個假對象。

這是您的測試應該如何看起來像：

// Arrange 
var sut = new ProductRepository(); //sut means System Under Test 
... 

// Act - select new product using SelectProduct method 
var result = sut.SelectProduct(product1.ProductId); 

// Assert 
.... 

假貨（或嘲弄）僅用於假貨之類的依賴性測試，而不是類本身。所以，在這個特定的測試中，你不需要使用模擬框架。