I recently ran into an issue where combining the DmarcDnsTestsMixin with

WebAPITestCase was causing very unusual failure cases, which could be

traced back to the cache. We have several things in our new expected

queries which rely on the cache being populated with certain data, but

the order in which things got initialized meant that the test case would

populate the cache, and then this mixin would clear it. We'd then see

extra queries popping up where we didn't expect them.
I've moved the parent class setUp to happen after we've cleared the

cache.

Ran unit tests everywhere.