Please run the tests

[Tim Penhey]

Hi all,

If you are hitting the magic merge it button on github because the
project isn't yet landed with the bot, please make sure you run the
tests before actually merging the code.

The juju/testing package didn't actually have passing tests, because
some tests were added that were missing a function call.

The fix has now landed, but please be very careful merging to master if
doing so manually.

Thank you,
Tim