Refactor Auth storage test

[wti806]

Hey there! So you want to contribute to a Firebase SDK?
Before you file this pull request, please read these guidelines:

Discussion

• Read the contribution guidelines (CONTRIBUTING.md).
• If this has been discussed in an issue, make sure to link to the issue here.
  If not, go file an issue about this before creating a pull request to discuss.

Testing

• Make sure all existing tests in the repository pass after your change.
• If you fixed a bug or added a feature, add a new test to cover your code.

API Changes

• At this time we cannot accept changes that affect the public API. If you'd like to help
  us make Firebase APIs better, please propose your change in an issue so that we
  can discuss it together.

[mikelehen]

You probably need to run "yarn" to get the new version of prettier so these diffs go away.

@jshcrowthe FYI- This sort of prettier version mismatch noise keeps coming up. I wonder if it'd make sense to do a version sanity-check in the automated prepush running of prettier.

[wti806]

@mikelehen Do I need to manually revert the prettier commit and push again after running yarn?

[mikelehen]

I think just running yarn and then doing a git push should revert the changes, since the pre-push hook will run prettier again and it should undo the changes.

[wti806]

Looks like the pre-pusher reverted the previous change in the new commit. Thank you so much @mikelehen

[jshcrowthe]

Thanks for this @mikelehen

[bojeil-google]

Changes look good. We just need to add the demo app changes. Shouldn't be launch blocking.