Commented Issue: Extend ShouldThrow*() to Func [12148]

Extend the ShouldThrow*() methods for Func<Task> too so you can work with async methods:

Func<Task> foo = async () => { await DoSthAsync(); }
foo.ShouldThrow<ArgumentNullException>();
Comments: Could it be also included in Windows Phone package? It'd be really useful for a asynchronous-like interface as WP. Currently, I see it is only available in WinRT.