TST: Add more tests for fixed issues
- [x] closes #11244
- [x] closes #11020
- [x] closes #12754
- [x] closes #12261
- [x] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`

thanks @mroeschke nice!