v2 testing documentation

[josh-chamberlain]

Context

follows #271

Requirements

• [ ] Set up documentation to ensure contributors are aware of the test database and how to interface with it.
• [ ] Add docstrings and additional documentation providing additional context when tests are run.

[josh-chamberlain]

@maxachis how much of this documentation would apply to other repos? I'm thinking we should have this figured out in advance of things like https://github.com/Police-Data-Accessibility-Project/data-source-identification/issues/49 so folks know how they should be writing tests

[maxachis]

@maxachis how much of this documentation would apply to other repos? I'm thinking we should have this figured out in advance of things like Police-Data-Accessibility-Project/data-source-identification#49 so folks know how they should be writing tests

@josh-chamberlain Here's what I think would generalize across repos:

1. The test database and how to access it
2. General principles for how to write tests
3. Libraries to be used when running tests (e.g., pytest)