New cop to ensure 'skip' has a message

[fatkodima]

Inspired by - https://hexdocs.pm/credo/Credo.Check.Design.SkipTestWithoutComment.html.

It is possible to skip a test without providing a reason why - https://github.com/minitest/minitest/blob/ed224bc9983eab31cbb4859f655daeec903da046/lib/minitest/assertions.rb#L783

Future you or other developers will have a hard time figuring out why it was skipped. So I suggest to enforce skip messages. Unless it is in condition already.

Example

# bad
skip

# good
skip("Is not supported by Active Record < 7")

# also good
skip if active_record_below_7?

[andyw8]

Seems like a useful cop 👍