Tests: Code Coverage Output

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This is cool. Not mocked but connecting to an actual staging github application using a personal access token and verifying the results. At some point would be useful to add coverage output.

Originally posted by @gitcoindev in #640 (comment)

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@gitcoindev perhaps you can add more details on what you envisioned? I can add to the spec and get it funded.

[gitcoindev]

@pavlovcik after the tests are run (E2E or unit), code coverage metrics can be calculated and a code coverage report can be generated. From the coverage reports one can see the percentage of code executed and which source code lines were executed during test execution. This then is a base to add new tests to cover scenarios that are not tested yet.