Increase code coverage to 100%

[sungam3r]

Current coverage is 71% - https://app.codecov.io/gh/destructurama/fsharp

[github-actions]

This issue was marked as stale since it has not been active for a long time

[github-actions]

This issue was marked as stale since it has not been active for a long time

[github-actions]

This issue was marked as stale since it has not been active for a long time