Detect unit tests and its coverage

[laurentsimon]

If we can, we should try to detect if the project uses unit testing, and the corresponding code coverage. May be done in combination with #78.

[laurentsimon]

we could start with simple heuristics: e.g. could count number of go files that have a corresponding _test.go.
Or look at other solution, like codecov.

[afmarcum]

Is this issue still needed or will it be covered by the Scorecard Golden testing effort?

[spencerschrock]

This is unrelated to golden testing, this refers to a new check suggestion.