TST: DataFrame initialization with an empty DataFrame with dtype
- [x] closes #20654
- [x] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them

Hello @gcaria! 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 2021-08-23 13:49:31 UTC Thanks for the help @jreback. 

However, it seems that pandas classes get capitalized in the test names (at least in this file), see the test just above (`test_constructor_DataFrame`) and the various `test_constructor_Series_...`. > Thanks for the help @jreback.
> 
> However, it seems that pandas classes get capitalized in the test names (at least in this file), see the test just above (`test_constructor_DataFrame`) and the various `test_constructor_Series_...`.

Thanks for the PR - should be lower case as Jeff suggest and per PEP8. Can you double check why CI is failing/merge master? This looks good to me otherwise :)  Thanks @alimcmaster1.Rebased to master and now all tests have passed thanks @gcaria 