Question

我有一个带有此操作的控制器UserController

// GET /blah
public Task<User> Get(string domainUserName)
{
        if (string.IsNullOrEmpty(domainUserName))
        {
            throw new ArgumentException("No username specified.");
        }

        return Task.Factory.StartNew(
            () =>
                {
                    var user = userRepository.GetByUserName(domainUserName);
                    if (user != null)
                    {
                        return user;
                    }

                    throw new HttpResponseException(Request.CreateErrorResponse(HttpStatusCode.NotFound, string.Format("{0} - username does not exist", domainUserName)));
                });
}

我正在尝试为我抛出404异常的情况编写测试。

以下是我尝试过的输出 -

1）

[Test]
public void someTest()
{
        var mockUserRepository = new Mock<IUserRepository>();
        mockUserRepository.Setup(x => x.GetByUserName(It.IsAny<string>())).Returns(default(User));
    var userController = new UserController(mockUserRepository.Object) { Request = new HttpRequestMessage() };

    Assert.That(async () => await userController.Get("foo"), Throws.InstanceOf<HttpResponseException>());
}

结果测试失败

  Expected: instance of <System.Web.Http.HttpResponseException>
  But was:  no exception thrown

2）

[Test]
public void someTest()
{
        var mockUserRepository = new Mock<IUserRepository>();
        mockUserRepository.Setup(x => x.GetByUserName(It.IsAny<string>())).Returns(default(User));
    var userController = new UserController(mockUserRepository.Object) { Request = new HttpRequestMessage() };

    var httpResponseException = Assert.Throws<HttpResponseException>(() => userController.Get("foo").Wait());
    Assert.That(httpResponseException.Response.StatusCode, Is.EqualTo(HttpStatusCode.NotFound));
}

结果测试失败

  Expected: <System.Web.Http.HttpResponseException>
  But was:  <System.AggregateException> (One or more errors occurred.)

3）

[Test]
public void someTest()
{
        var mockUserRepository = new Mock<IUserRepository>();
        mockUserRepository.Setup(x => x.GetByUserName(It.IsAny<string>())).Returns(default(User));
    var userController = new UserController(mockUserRepository.Object) { Request = new HttpRequestMessage() };

    var httpResponseException = Assert.Throws<HttpResponseException>(async () => await userController.Get("foo"));
    Assert.That(httpResponseException.Response.StatusCode, Is.EqualTo(HttpStatusCode.NotFound));
}

结果测试失败

  Expected: <System.Web.Http.HttpResponseException>
  But was:  null

4）

[Test]
[ExpectedException(typeof(HttpResponseException))]
public async void ShouldThrow404WhenNotFound()
{            var mockUserRepository = new Mock<IUserRepository>();
        mockUserRepository.Setup(x => x.GetByUserName(It.IsAny<string>())).Returns(default(User));

    var userController = new UserController(mockUserRepository.Object) { Request = new HttpRequestMessage() };

    var task = await userController.Get("foo");
}

结果测试通过

问题 -

当ExpectedException出现时，为什么Assert.Throws不会处理HttpResponseException？
我不想只测试抛出异常。我想在响应的状态代码上断言。这样做的方法是什么？

对这些行为及其原因的任何比较都会很棒！

Answer 1

您看到了由async void引起的问题。

特别是：

1）async () => await userController.Get("foo")转换为TestDelegate，返回void，因此您的lambda表达式被视为async void。因此测试运行器将开始执行lambda但不等待它完成。 lambda在Get完成之前返回（因为它是async），并且测试运行器看到它返回时没有异常。

2）Wait包含AggregateException中的所有例外。

3）同样，async lambda被视为async void，因此测试运行器不会等待它的完成。

4）我建议您使用async Task而不是async void，但在这种情况下，测试运行器会等待完成，从而看到异常。

根据this bug report，在NUnit的下一个版本中有一个修复。在此期间，您可以构建自己的ThrowsAsync方法; example for xUnit is here。

Answer 2

我不确定它何时被添加，但当前版本的Nunit（撰写本文时为3.4.1）包含ThrowsAsync方法

请参阅https://github.com/nunit/docs/wiki/Assert.ThrowsAsync

示例：

[Test]
public void ShouldThrow404WhenNotFound()
{
    var mockUserRepository = new Mock<IUserRepository>();
    mockUserRepository.Setup(x => x.GetByUserName(It.IsAny<string>())).Returns(default(User));
    var userController = new UserController(mockUserRepository.Object) { Request = new HttpRequestMessage() };

    var exception = Assert.ThrowsAsync<HttpResponseException>(() => userController.Get("foo"));

    Assert.That(exception.Response.StatusCode, Is.EqualTo(HttpStatusCode.NotFound));
}

Answer 3

This blog谈论与我类似的问题。

我按照那里提出的建议，进行了这样的测试 -

    [Test]
    public void ShouldThrow404WhenNotFound()
    {
        var mockUserRepository = new Mock<IUserRepository>();
        mockUserRepository.Setup(x => x.GetByUserName(It.IsAny<string>())).Returns(default(User));
        var userController = new UserController(mockUserRepository.Object) { Request = new HttpRequestMessage() };

        var aggregateException = Assert.Throws<AggregateException>(() => userController.Get("foo").Wait());
        var httpResponseException = aggregateException.InnerExceptions
            .FirstOrDefault(x => x.GetType() == typeof(HttpResponseException)) as HttpResponseException;

        Assert.That(httpResponseException, Is.Not.Null);
        Assert.That(httpResponseException.Response.StatusCode, Is.EqualTo(HttpStatusCode.NotFound));
    }

我对它不太满意，但这很有效。

编辑1

受@StephenCleary的启发，我添加了一个静态助手类来完成我正在寻找的断言。它看起来像这样 -

public static class AssertEx
{
    public static async Task ThrowsAsync<TException>(Func<Task> func) where TException : class
    {
        await ThrowsAsync<TException>(func, exception => { });
    } 

    public static async Task ThrowsAsync<TException>(Func<Task> func, Action<TException> action) where TException : class
    {
        var exception = default(TException);
        var expected = typeof(TException);
        Type actual = null;
        try
        {
            await func();
        }
        catch (Exception e)
        {
            exception = e as TException;
            actual = e.GetType();
        }

        Assert.AreEqual(expected, actual);
        action(exception);
    }
}

我现在可以进行类似的测试 -

    [Test]
    public async void ShouldThrow404WhenNotFound()
    {
        var mockUserRepository = new Mock<IUserRepository>();
        mockUserRepository.Setup(x => x.GetByUserName(It.IsAny<string>())).Returns(default(User));
        var userController = new UserController(mockUserRepository.Object) { Request = new HttpRequestMessage() };

        Action<HttpResponseException> asserts = exception => Assert.That(exception.Response.StatusCode, Is.EqualTo(HttpStatusCode.NotFound));
        await AssertEx.ThrowsAsync(() => userController.Get("foo"), asserts);
    }

Answer 4

如果等待任务，则抛出的异常将聚合到AggregateException中。您可以检查AggregateException的内部异常。这可能是案例2不起作用的原因。

在任务中运行的用户代码抛出的未处理异常将传播回加入线程，但本主题后面描述的某些方案除外。当您使用静态或实例Task.Wait或Task.Wait方法之一时，会传播异常，并通过将调用封装在try-catch语句中来处理它们。如果任务是附加子任务的父项，或者您正在等待多个任务，则可能会抛出多个异常。要将所有异常传播回调用线程，Task infrastructure将它们包装在AggregateException实例中。 AggregateException有一个InnerExceptions属性，可以枚举该属性以检查抛出的所有原始异常，并单独处理（或不处理）每个异常。即使只抛出一个异常，它仍然包含在AggregateException中。

Link to MSDN

Answer 5

我在方案3中遇到类似的问题测试用例由于以下结果而失败

Expected: <UserDefineException>
But was:  null

使用Assert.ThrowAsync＆lt;＆gt;问题得到解决

我的Web API操作方法和单元测试用例方法如下

public async Task<IHttpActionResult> ActionMethod(RequestModel requestModel)
{
   throw UserDefineException();
}


[Test]
public void Test_Contrller_Method()
{
   Assert.ThrowsAsync<UserDefineException>(() => _controller.ActionMethod(new RequestModel()));
}

Answer 6

这是文档中的示例：

var ex = Assert.ThrowsAsync<ArgumentException>(async () => await MethodThatThrows());

使用ThrowsAsync
使用async / await

https://docs.nunit.org/articles/nunit/writing-tests/assertions/classic-assertions/Assert.ThrowsAsync.html

Nunit异步测试异常断言

6 个答案: