How to write unit tests with TPL and TaskScheduler

Answer 1

For at least most simple-ish cases, I like to use an "expiring" assertion for this sort of thing. e.g.:

YourCollection sut = new YourCollection();

object newItem = new object();
sut.Add(newItem);

EventualAssert.IsTrue(() => sut.Contains(newItem), TimeSpan.FromSeconds(2));

where EventualAssert.IsTrue() looks something like this:

public static void IsTrue(Func condition, TimeSpan timeout)
{
    if (!SpinWait.SpinUntil(condition, timeout))
    {
        Assert.IsTrue(condition());
    }
}

I also generally add an override with a default timeout which I use for most of my tests, but ymmv...