Develop Tests

[sco1]

Initial functionality for this package was only evaluated against a basic sample file. Before this goes live to PyPi, more comprehensive testing should be developed to ensure we're appropriately covering as many scenarios as possible.

The currently brainstormed testing points:

• Argument parsing
• Warning classification
• Emitting correct line & column numbers
• Formatting warning message with argument name (where relevant)
• Outputting correct tuple for flake8

Once these are all implemented there are a couple follow-on housekeeping items:

• Update README
• Add testing to CI pipeline