Need to add more unit tests

[nusbaume]

The history_output repo now as the ability to run Fortran unit tests via a Github Action workflow. However, only a few tests were actually written to demonstrate feasibility, which means most of the code has no unit test coverage. Thus it would be good to significantly increase the number of unit tests so that we can have increased confidence that everything is working as expected.

Also, the current Github workflow YAML file references the sima-history branch. However that branch doesn't actually exist on this repo, and so it would probably be better to replace it with development, or simply allow it for all relevant branch pushes.