Added two tests for issue #29697
I added two basic tests for `merge` as requested in #29697, one for `how="outer"` and one for  `how="right"`. 

I'm not sure if the way I'm creating duplicate columns for the `expected` dataframe is the recommended way but I could not find anything on this. Please let me know if there's a better way to do this.

- [x] closes #29697
- [x] 2 tests added / 2 passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`




Think the best place in the file for this test method would be directly after `def test_merge_suffix` > Think the best place in the file for this test method would be directly after `def test_merge_suffix`

I gave it a look and I agree. Moved it in the latest commit. Hello @devjeetr! Thanks for updating this PR. We checked the lines you've touched for [PEP 8](https://www.python.org/dev/peps/pep-0008) issues, and found:



There are currently no PEP 8 issues detected in this Pull Request. Cheers! :beers: 

##### Comment last updated at 2020-04-23 18:29:46 UTC LGTM please fix up the pep8 issues for CI to pass. @devjeetr  force-pushed a lint fixup thanks @devjeetr 