Need better unit-test coverage

[ryan-collingham]

We have good coverage with our functional tests but our unit-testing is currently better in some areas than others. Ideally we should aim for as close to 100% code coverage as reasonably possible with unit tests alone, with a unit test corresponding to every non-trivial testplan module.

[ryan-collingham]

Our current code coverage for unit tests is 57% as measured by pytest-cov.

[ryan-collingham]

I'm only considering python code for this issue, not JS code for the web UI.