Question

Consider this unit test:

    [TestMethod]
    public void QueueManager_OnNextItem()
    {
        bool called = false;
        var queue = new QueueManager<int>(
                        new Moq.Mock<ILogger>().Object, 
                        new Moq.Mock<IItemQueueManagerPerformanceTracker>().Object);

        queue.OnNextItem += i => { called = true; };

        queue.Add(1);
        queue.Start();

        //need to RELIABLY wait here

        Assert.IsTrue(called);
    }

QueueManager has a worker thread running internally (Start() kicks it off) which dequeues an item and calls OnNextItem.

As this test stands it will always always fail, as the Assert... is called before there is a context switch, to allow called = true to be executed.

I did place a Thread.Sleep(blah) prior to the Assert....

This does work when the test is run in isolation.

However, run it will the other load of unit tests and I found I was being presented with the good old…

the agent process was stopped while the test was running

…which has no immediate resolution Unit Testing – The agent process was stopped while the test was running. and leaves you exposed to VS 2010 Test Runner error “The agent process was stopped while the test was running.”

So, in light of that…what approach can I use to ensure that I test that my event is being fired AND it is reliable so as not to bork my build process?

TIA

Answer 1

One option is to make the OnNextItem responsible for unblocking:

// Setup as before
object monitor = new object();
queue.OnNextItem += i => { lock(monitor) { Monitor.Pulse(monitor); }};

lock (monitor)
{
    queue.Add(1);
    queue.Start();
    Assert.IsTrue(Monitor.Wait(monitor, 1000));
}

That will wait up to one second for OnNextItem to be called, and fail if the wait times out.