Speed up tests
- Previously tests set up a new app with a full yarn install just to get a mock server to talk to
- Only one out of 214 tests used the response from the server
- Mocking the API responses reduced the test run time from >1m30s to <8s
- Removed 400+ lines of test helpers
- Coverage is identical
- Also converted the tests I edited to async/await style
I appreciate there's a lot to review in this MR. The two commits are logically separated so it may help to review them independently.
Edited by Tamlyn Rhodes