look ma no null reference exceptions!

nonullrefexceptions.cs

    public class When_blah
    {
        static string s;

        Establish that = () =>  s = null;
        Because of = () => s= s.MyExt();
        It should_be_null = () => s.ShouldBeNull();
    }

    public static class  MyExts
    {
        public static string MyExt(this string s)
        {
            return s;
        }
    }