More extensive docstring for base test case classes.
More extensive docstring for base test case classes.

bobsilverberg/moztrap,mccarrmb/moztrap,shinglyu/moztrap,bobsilverberg/moztrap,mccarrmb/moztrap,shinglyu/moztrap,shinglyu/moztrap,bobsilverberg/moztrap,mozilla/moztrap,mozilla/moztrap,mozilla/moztrap,shinglyu/moztrap,mccarrmb/moztrap,bobsilverberg/moztrap,mozilla/moztrap,mccarrmb/moztrap,mozilla/moztrap,mccarrmb/moztrap,shinglyu/moztrap