c# - 对从线程触发的事件进行单元测试

Question

我在对一个类进行单元测试时遇到问题，该类会在线程启动和结束时触发事件。有问题的来源的简化版本如下:

public class ThreadRunner
{
    private bool keepRunning;

    public event EventHandler Started;
    public event EventHandler Finished;

    public void StartThreadTest()
    {
        this.keepRunning = true;
        var thread = new Thread(new ThreadStart(this.LongRunningMethod));
        thread.Start();
    }

    public void FinishThreadTest()
    {
        this.keepRunning = false;
    }

    protected void OnStarted()
    {
        if (this.Started != null)
            this.Started(this, new EventArgs());
    }

    protected void OnFinished()
    {
        if (this.Finished != null)
            this.Finished(this, new EventArgs());
    }

    private void LongRunningMethod()
    {   
        this.OnStarted();

        while (this.keepRunning)
            Thread.Sleep(100);

        this.OnFinished();
    }
}

然后我有一个测试来检查 Finished 事件是否在 LongRunningMethod 完成后触发，如下所示:

[TestClass]
public class ThreadRunnerTests
{
    [TestMethod]
    public void CheckFinishedEventFiresTest()
    {
        var threadTest = new ThreadRunner();

        bool finished = false;

        object locker = new object();

        threadTest.Finished += delegate(object sender, EventArgs e)
        {
            lock (locker)
            {
                finished = true;
                Monitor.Pulse(locker);
            }
        };

        threadTest.StartThreadTest();
        threadTest.FinishThreadTest();

        lock (locker)
        {
            Monitor.Wait(locker, 1000);
            Assert.IsTrue(finished);
        }
    }
}

所以这里的想法是，在检查是否设置了 finished 标志之前，测试将最多阻塞一秒钟 - 或者直到触发 Finish 事件.

显然我做错了什么，因为有时测试会通过，有时不会。调试似乎非常困难，而且我希望遇到的断点(例如 OnFinished 方法)似乎并不总是如此。

我假设这只是我对线程工作方式的误解，所以希望有人能启发我。

Answer 1

锁在这里不合适，您需要发出事件信号。例如:

    public void CheckFinishedEventFiresTest() {
        var threadTest = new ThreadRunner();
        var finished = new ManualResetEvent(false);
        threadTest.Finished += delegate(object sender, EventArgs e) {
            finished.Set();
        };
        threadTest.StartThreadTest();
        threadTest.FinishThreadTest();
        Assert.IsTrue(finished.WaitOne(1000));
    }