测试在异步控制器操作中设置了线程文化

Question

我正在尝试迁移一个 asp.net mvc 5 控制器以使用 async/await。我在测试是否设置了正确的文化时遇到了问题。

在旧（非异步）版本的代码中，单元测试通过，因为一切都在同一个线程上运行。在新（异步）版本的代码中，单元测试失败，因为在调用 async/await 方法后未维护当前区域性。

在新版本的代码中，文化设置正确，视图有正确的文化设置。唯一的问题是我无法在我的 NUnit 测试中对此进行测试，因为它在 await 调用之外。

你知道我该如何解决这个问题吗？我在下面使用的代码提供了一个类似伪代码的版本。

旧代码：

public ActionResult Index()
{
    // Look up user in database
    var dbUser = database.GetUser(User.Identity.GetUserId());

    // Set preferred culture
    Thread.CurrentThread.CurrentCulture = new CultureInfo(dbUser.PreferredCulture);
    Thread.CurrentThread.CurrentUICulture = new CultureInfo(dbUser.PreferredCulture);

    // Do some other work
    DoSynchronousWork();

    return View();
}

[TestFixture]
public class TestClass
{
    [Test]
    public void TestIndex_CorrectCulture()
    {
        // Mock database
        database.GetUser().Returns(new User(){PreferredCulture = "de"});

        // Call controller
        _controller.Index();

        // Check that the thread culture was correctly set - this passes
        Assert.AreEqual("de", Thread.CurrentThread.CurrentCulture);
        Assert.AreEqual("de", Thread.CurrentThread.CurrentUICulture);
    }
}

新代码：

public async Task<ActionResult> Index()
{
    // Look up user in database
    var dbUser = database.GetUser(User.Identity.GetUserId());

    // Set preferred culture
    Thread.CurrentThread.CurrentCulture = new CultureInfo(dbUser.PreferredCulture);
    Thread.CurrentThread.CurrentUICulture = new CultureInfo(dbUser.PreferredCulture);

    // Do some other work
    await DoAsynchronousWork();

    return View();
}

[TestFixture]
public class TestClass
{
    [Test]
    public async Task TestIndex_CorrectCulture()
    {
        // Mock database
        database.GetUser().Returns(new User(){PreferredCulture = "de"});

        // Call controller
        await _controller.Index();

        // Check that the thread culture was correctly set - this fails because the culture inside _controller.Index() is lost after the await call
        Assert.AreEqual("de", Thread.CurrentThread.CurrentCulture);
        Assert.AreEqual("de", Thread.CurrentThread.CurrentUICulture);
    }
}

Answer 1

如果您使用的是模拟库，请尝试将不可测试的代码移至服务：

interface IThreadCultureSetter
{
    void SetCurrentThreadCulture(CultureInfo ci, [CallerMemberName]string callerMethod = null);
}

class ThreadCultureSetter : IThreadCultureSetter
{
    public void SetCurrentThreadCulture(CultureInfo ci, [CallerMemberName]string callerMethod = null)
    {
        // Set thread culture
    }
}

更改您的控制器操作以使用该界面：

private readonly IThreadCultureSetter _cultureSetter;

public async Task<ActionResult> Index()
{
    // Look up user in database
    var dbUser = database.GetUser(User.Identity.GetUserId());

    // Set preferred culture
    _cultureSetter.SetCurrentThreadCulture(new CultureInfo(dbUser.PreferredCulture));

    // Do some other work
    await DoAsynchronousWork();

    return View();
}

在您的测试中，提供一个模拟的IThreadCultureSetter 并验证该方法是否使用所需的CultureInfo 调用：

// Assume you use Moq
Mock<IThreadCultureSetter> cultureSetterMock;

// The SetCurrentThreadCulture must be called by Index method
mock.Verify(x => x.SetCurrentThreadCulture(It.Is<CultureInfo>(ci => ci.Name == "de"), "Index"));

事实上，Thread.CurrentThread.CurrentCulture 是异步静态的（值存储在 AsyncLocal 中）并且对测试不友好，因为它的值仅存在于当前捕获的异步范围内。

更新

我刚刚发现可以使用自定义 SynchronizationContext 来测试线程文化设置（无法保证）是否符合预期的文化：

class ThreadCultureInspectionSynchronizationContext : SynchronizationContext
{
    private readonly string _expectedCultureName;

    public ThreadCultureInspectionSynchronizationContext(string expectedCultureName)
    {
        _expectedCultureName = expectedCultureName;
    }

    public bool WasSetToExpected { get; private set; }

    public override void Post(SendOrPostCallback d, object state)
    {
        // When context is switching, e.g. continuation of an await being executed, this method is called.
        // This method could inspect on thread culture, and set flag to true once expected culture detected.
        // This method can only prove that the thread culture was set, but cannot suggest by which method.

        if (!WasSetToExpected)
        {
            WasSetToExpected = Thread.CurrentThread.CurrentCulture.Name.Dump() == _expectedCultureName;
        }

        base.Post(d, state);
    }
}

在你的测试中，在调用Index之前：

var ctx = new ThreadCultureInspectionSynchronizationContext("de");
SynchronizationContext.SetSynchronizationContext(ctx);
await Index();
...
Assert.IsTrue(ctx.WasSetToExpected);

如果您的线程文化是由Index 方法设置的，您会看到同步上下文对线程文化的所有检查都是您所期望的。