Increase test coverage

Part of #40 .
Yes, if it was `any*` you would need the check.

As for the user of "power" in most of the rules, it corresponds to http://hg.python.org/cpython/file/9efefcab817e/Grammar/Grammar#l102 in the grammar. So from a parser POV it does relate to power from math, but that's just because of precedence rules.