Hound warnings on JS test files

[maxbeatty]

I've opened a few PRs and each gets lots of comments from @houndci-bot because the JS unit test files do not conform to the ESLint settings. Here are few ways I've considered addressing this:

1. Ignore the test files similar to Fix Hound warnings for minified files. #20446. This is the least amount of work and will get other PRs passing and more likely to merge.
2. Fix the eslint issues in the test files, add a grunt task or npm script (v4: Move to npm scripts #20332) to transpile the test files, and update the references in index.html. This is obviously more work but would be more of a long term benefit.

I'm open to other ways to please @houndbot-ci when changing JS test files and willing to put in the work 😅

[bardiharborow]

@maxbeatty just an update on this. Once #21005 merges, Travis will lint tests correctly. Hound is still mad because of houndci/hound#889, but that's more annoying than show-stopping for now.

[mdo]

Closing out given latest comment from @bardiharborow. Holler if this needs to be re-opened to track anything else not already covered in another issue or PR <3.