The static functions added currently belong to JOAuth2ClientTest. This means that whilst the unit tests pass as a group if you run this class isolated then it fails because none of the functions exist.
The entire JGoogleAuthOauth2Test class needs a bigger overhaul to mock more of the functionality - but this at least isolates the test class
You can test by running the JGoogleAuthOauth2Test on it's own. Before this change it will fail - after it will pass