Clean up tests using DynamicData

[gfs]

https://learn.microsoft.com/en-us/visualstudio/test/how-to-create-a-data-driven-unit-test?view=vs-2022

Tests could be simplified by consolidating the many copies of the test data rows, also simplifying adding new tests for new formats. See https://learn.microsoft.com/en-us/visualstudio/test/how-to-create-a-data-driven-unit-test?view=vs-2022#member-data-driven-test.

[gfs]

Partially implemented in #114 for the expected num files tests. The remainder of the tests don't generally share exactly the same arguments so there is more limited room to use dynamic data other than in the CLI tests for expected num files.