...instead of just throwing the payload directly. This improves twot things:
It's nicer to use.
myThing.expect('should have blah')instead of
myThing.expect(new Error('should have blah')).
It saves overhead. Putting
new Error(message)always creates the error,
including generating the stacktrace and everything. Boo. I haven't actually
measured it, but if that was hurting before, it shouldn't any more.