模拟了一个返回 true 的方法仍然返回 false答案

【问题标题】：Mocked a method to return true still returns false模拟了一个返回 true 的方法仍然返回 false
【发布时间】：2021-04-01 07:25:41
【问题描述】：

我有一个这样的控制器方法：

public class ValuesController : Controller
{
    private readonly IService fService;
    public ValuesController( IService fService)
    {
        this.fService = fService;            
    }

    public IActionResult InsertDetails( [FromForm]Details details, IFormFile file)
    {
        bool result = fService.SaveDetails(details, file);
        return OK();
    }
}

测试这个控制器的测试用例如下：

public class ValuesControllerTests
{
     readonly Mock<IService> mockService = new Mock<IService>();
     
     [TestMethod]
     public void SaveDetails_Test_Success()
     {
         var details = GetMockDetails(); // gets the sample DTO values
         mockService.Setup(x => x.SaveDetails(details, GetFile())).Returns(true); ---- this is returning false even after mocking the value
         var controller = new ValuesController(mockService.Object);
         controller.ControllerContext.HttpContext = new DefaultHttpContext();
         var res = controller.InsertDetails(details, GetFile()) as OkObjectResult;
         Assert.AreEqual("File Details Saved Successfully", res.Value.ToString());
         Assert.AreEqual(200, res.StatusCode);
     }

     IFormFile GetFile()
     {
         return new FormFile(new MemoryStream(Encoding.UTF8.GetBytes("This is a dummy file")), 0, 0, "Data", "dummy.txt");
     }
}

即使我将方法 SaveDetails 模拟为返回 true，它总是返回 false。
谁能告诉我我在这里做错了什么？非常感谢。

【问题讨论】：

标签： mocking asp.net-core-webapi moq vs-unit-testing-framework

【解决方案1】：

期望设置的IFormFile（引用/实例）与调用被测成员时使用的不同。这会导致模拟返回被调用成员的默认值，即false，因为它是一个布尔值。

当GetFile()被调用时，每次都会返回一个新的实例。

所以要么使用相同的实例，就像 details 所做的那样

public void SaveDetails_Test_Success() {
    Details details = GetMockDetails();
    IFormFile file = GetFile(); //single instance
    mockService.Setup(x => x.SaveDetails(details, file)).Returns(true); //used here
    ValuesController controller = new ValuesController(mockService.Object);
    controller.ControllerContext.HttpContext = new DefaultHttpContext();
    var res = controller.InsertDetails(details, file) as OkObjectResult; //and here
    Assert.AreEqual("File Details Saved Successfully", res.Value.ToString());
    Assert.AreEqual(200, res.StatusCode);
 }

或者使用像It.IsAny<>()这样的参数匹配器来放松期望

public void SaveDetails_Test_Success() {
    Details details = GetMockDetails();
    mockService.Setup(x => x.SaveDetails(details, It.IsAny<IFormFile>())).Returns(true); //<-- NOTE
    ValuesController controller = new ValuesController(mockService.Object);
    controller.ControllerContext.HttpContext = new DefaultHttpContext();
    var res = controller.InsertDetails(details, GetFile()) as OkObjectResult; 
    Assert.AreEqual("File Details Saved Successfully", res.Value.ToString());
    Assert.AreEqual(200, res.StatusCode);
 }

【讨论】：

【解决方案2】：

您的Setup 的问题在于它过于具体。
请记住，参数匹配基于类的引用检查。

mockService
      .Setup(service => service.SaveDetails(It.IsAny<Details>(), It.IsAny<IFormFile>()))
      .Returns(true);

如果您想验证通话，则需要
保存GetFile 的结果，然后进行断言：

public void SaveDetails_Test_Success()
{
    //Arrange
    var details = GetMockDetails(); 
    var file = GetFile(); //same instance is used everywhere

    mockService
      .Setup(x => x.SaveDetails(It.IsAny<Details>(), It.IsAny<IFormFile>()))
      .Returns(true); 

    var controller = new ValuesController(mockService.Object);
    controller.ControllerContext.HttpContext = new DefaultHttpContext();
    
    //Act
    var result = controller.InsertDetails(details, file);
    
    //Assert
    var res = Assert.IsAssignableForm<OkObjectResult>(result); //Here we test the assignability as well
    Assert.AreEqual("File Details Saved Successfully", res.Value.ToString());
    //Assert.AreEqual(200, res.StatusCode); //This assert is unnecessary

    mockService
      .Verify(x => x.SaveDetails(details, file), Times.Once); 
}

我建议不要将控制器操作的响应强制转换为 OkObjectResult。（就像我在上面的测试用例中所做的那样）

【讨论】：