Increase test coverage

[davidcollom]

There is currently only 38% total test coverage, to help improve collaboration and ensure a stable experience we should look to increase this (target TBA) significantly.

This should also be enforced within GitHub Actions and can be updated here: https://github.com/jetstack/version-checker/blob/b27e0afd5d5cfc517d0139061fe5a105e8eee7b0/.testcoverage.yml

[github-actions]

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