Tests: show any and all actual/expected values

[timmywil]

Summary

• Show actual and expected values even if they are falsey.
• Also leave out message if none was provided, rather than printing undefined.

Checklist

• [x] New tests have been added to show the fix or feature works
• [x] If needed, a docs issue/PR was created at https://github.com/jquery/api.jquery.com