Example usage of an async lambda.

Async-Lambda.cs

Assert.Throws<SomeException>(async () => await obj.GetAsync());

I saw some code that suggested to me that not everyone knows how you pass an await call as a lambda expression. It turns out the async keyword can apply to a lambda expression as well.

Unless Assert.Throws takes a Func of Task instead of Action the compiler interprets the lambda as an async void method. This means it can't "await" the lambda and discover the exception.

Thanks nigel! I saw the same thing here: http://blogs.msdn.com/b/pfxteam/archive/2012/02/08/10265476.aspx

Somewhat related, I started hacking on a library to make testing Tasks better... https://github.com/pprovost/assertex

Goddamn it, its not on NuGet. I'll go stand in the corner until I've fixed that...

How's this? https://gist.github.com/4616366

Just pushed AssertEx up to NuGet. Here's a teaser:

If you want to inspect the Task:

public class Subject
{
    public Task GetAsync()
    {
        return Task.Run(() => { throw new SomeException(); });
    }
}

...

AssertEx.TaskThrows<SomeException>(obj.GetAsync);

I need to write up a decent wiki on how to test async code - all the horrors are coming back to me now...