Make tests less brittle and more broad in coverage #61
Description
This is a bit of housekeeping.
Many of the unit tests index on REST API v2 testing, and make assertions that go several levels deep in the stack. Since many of them were initially written, the underlying / intermediate functionality has been modularized and refactored out.
While this has been useful for ensuring the safety and backwards compatibility of the multiple refactors that the library has undergone, e.g. by writing expectations around the behavior of descendant classes to test integration / implementation of the abstract base classes, we need broader and more generic coverage at this point so that each expectation is tested in the appropriate place, e.g. concerns of ApiClient are tested in a dedicated test with a model subclass of the abstract base class versus indirectly asserted in tests of RestApiV2Client.