Add test to validate resampling GH9915
- [x] closes #9915
- [x] tests added / passed
- [x] passes `git diff upstream/master | flake8 --diff`
- [ ] whatsnew entry

This shows `FutureWarning: .resample() is now a deferred operation use .resample(...).mean() instead of .resample(...)` in the IDE ...
 lgtm. ping when green.
 thanks!
