如何使用 ActionResult<T> 进行单元测试? [英] How to Unit Test with ActionResult&lt;T&gt;?

问题描述

我有一个 xUnit 测试，例如:

I have a xUnit test like:

[Fact]
public async void GetLocationsCountAsync_WhenCalled_ReturnsLocationsCount()
{
    _locationsService.Setup(s => s.GetLocationsCountAsync("123")).ReturnsAsync(10);
    var controller = new LocationsController(_locationsService.Object, null)
    {
        ControllerContext = { HttpContext = SetupHttpContext().Object }
    };
    var actionResult = await controller.GetLocationsCountAsync();
    actionResult.Value.Should().Be(10);
    VerifyAll();
}

来源是

/// <summary>
/// Get the current number of locations for a user.
/// </summary>
/// <returns>A <see cref="int"></see>.</returns>
/// <response code="200">The current number of locations.</response>
[HttpGet]
[Route("count")]
public async Task<ActionResult<int>> GetLocationsCountAsync()
{
    return Ok(await _locations.GetLocationsCountAsync(User.APropertyOfTheUser()));
}

结果的值为空，导致我的测试失败，但是如果您查看 ActionResult.Result.Value(内部属性)，它包含预期的解析值.

The value of the result is null, causing my test to fail, but if you look at ActionResult.Result.Value (an internal property) it contains the expected resolved value.

请参阅以下调试器的屏幕截图.

See the following screen capture of the debugger.

如何让 actionResult.Value 填充到单元测试中?

How do I get the actionResult.Value to populate in a unit test?

推荐答案

在运行时，由于隐式转换，您的原始测试代码仍然可以工作.

At run time your original code under test would still work because of the implicit conversion.

但根据提供的调试器图像，测试似乎对结果的错误属性进行了断言.

But based on the provided debugger image it looks like the test was asserting on the wrong property of the result.

因此，虽然更改被测方法允许测试通过，但无论哪种方式都可以实时运行

So while changing the method under test allowed the test to pass, it would have worked when run live either way

ActioResult 有两个属性，根据使用它的操作返回的内容进行设置.

ActioResult<TValue> has two properties that are set depending on what is returned from the action that uses it.

/// <summary>
/// Gets the <see cref="ActionResult"/>.
/// </summary>
public ActionResult Result { get; }

/// <summary>
/// Gets the value.
/// </summary>
public TValue Value { get; }

来源

因此，当控制器操作使用 Ok() 返回时，它将通过隐式转换设置操作结果的 ActionResult.Result 属性.

So when the controller action returned using Ok() it would set the ActionResult<int>.Result property of the action result via implicit conversion.

public static implicit operator ActionResult<TValue>(ActionResult result)
{
    return new ActionResult<TValue>(result);
}

但是测试是断言 Value 属性(参考 OP 中的图像)，在这种情况下没有设置.

But the test was asserting the Value property (refer to image in OP), which in this case was not being set.

无需修改被测代码以满足测试，它可以访问 Result 属性并对该值进行断言

Without having to modify the code under test to satisfy the test it could have accessed the Result property and make assertions on that value

[Fact]
public async Task GetLocationsCountAsync_WhenCalled_ReturnsLocationsCount() {
    //Arrange
    _locationsService
        .Setup(_ => _.GetLocationsCountAsync(It.IsAny<string>()))
        .ReturnsAsync(10);
    var controller = new LocationsController(_locationsService.Object, null) {
        ControllerContext = { HttpContext = SetupHttpContext().Object }
    };

    //Act
    var actionResult = await controller.GetLocationsCountAsync();

    //Assert
    var result = actionResult.Result as OkObjectResult;
    result.Should().NotBeNull();
    result.Value.Should().Be(10);

    VerifyAll();
}

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