Clean up `test_coverage_table_spec` to use more mock data
Summary
The test_coverage_table_spec.js file is fairly messy. It repeats a lot of code that would be better suited in a mock data file or frontend fixture.
Improvements
Small changes to remove duplicate code when setting up states to test.
Risks
We could miss a test case that we were testing before the refactor, but there aren't many tests in this file so we should be okay.
Involved components
Optional: Intended side effects
Make updating this file a lot easier and the tests easier to understand.