Tests for frame extraction

[sfmig]

Integration tests for frame extraction.

Closes #15

[samcunliffe]

All looks good. 🫐

My comments are mostly questions. I have no substantive comments on the tests themselves.

• You're missing a few test_flibble() -> None: typehints. Don't know if they're important in tests but you have some typehints just not everywhere.
• The file is quite long. Is there a smart way to break it up? Things that come to mind:
  • Remove Parameters from the docstrings for tests?
  • Make more explicit test function names so you can do away with docstrings altogether?!
  • cough longer line length cough in the linter.

[sfmig]

thanks for the feedback @samcunliffe!
I reduced the length of the tests file by:

• reducing docstrings in fixtures and tests,
• factoring out the fixtures, and
• using parametrisation to combine the tests that run the CLI app with and without CLI inputs.

I think it looks a bit more neat, with the caveat that now I am using the mocked app in both test cases, so in one case (the empty CLI args case) I'm unnecessarily detaching from the real use case. Let me know any thoughts!