Clean up feeds and improve test coverage

This is a fairly hefty PR to start improving our test coverage in our feeds as well as ensure errors are properly being handled.

There are quite a few fixtures which I created, hopefully what I can now do is setup fixturator to properly generate these but they will be in a separate PR.
Feed is now called `mock_static_feed` but still contains Cake as it is unlikely to be found in a normal feed and thus is a good quick test for this.

Also, :cake: