Maintenance: Restructure tests

[heitorlessa]

Problem: As more utilities were added such as Parser and Event source data classes, we have duplicated fixtures along with helper functions to retrieve event samples.

We should restructure our tests to make better use of conftest, and optionally clean up any test names/similar tests

[michaelbrewer]

@heitorlessa i do like the idea of having a directory of example events json for the fixtures (but also in general uses)