Change RSpec output format

The doc format is a little more verbose, making it easier to see what is
going on as the test is running.

Also threw in some colours because I like colours.
Make the tests more explicit

One can take DRY a little too far, and I think this is better as it's
hard to make the tests completely "dynamic", so if you change the
payload then the tests always pass (as long as the payload is valid).
Test that metrics are being marked
Test that behaviour is correct for invalid log IDs