(maint) Spec improvements

This PR includes 2 spec improvements. The first involves finishing an incomplete test. The second involves abstractive the setup and teardown of some of the example groups.

The updated test here was never finished. It set expectations without
invoking any methods. This commit fixes a bug about which namespace
would receive the git_sha_or_tag method and adds a method call to test
the behavior.

Using rspec's around syntax vastly simplifies teardown and setup in
tests that require setting and later resetting variables. This commit
updates several examples in the config spec to use this syntax.