Added runTests to simplify usage in interactive mode

[sporring]

In interactive mode, it is superfluous to give default empty parameters. Thus I propose runTests

[farlee2121]

This is something that caused me to double take when I first started with the library.

I feel like this is a fairly high-traffic API decision though, and @haf should have the final call.

[haf]

I think it sounds like a great change!