Simplify tests.

[reitermarkus]

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Extracted from #16629 to see if any of these changes cause the flaky tests.

[apainintheneck]

Looks good to me. At a glance, it doesn't seem to increase test time noticeably and it makes the tests easier to follow. It also better insulates tests from each other by clearing the tap caches.

[apainintheneck]

I wonder if we could just include this in the glob pattern itself. Doesn't need to be changed though. This is fine.

[p-linnane]

This may be causing some brew style errors. It appears it's not respecting the sharding we did of the cask repo:
https://github.com/Homebrew/homebrew-core/actions/runs/7861902512/job/21452740091?pr=162322#step:3:35

[apainintheneck]

Interesting... I wouldn't expect this to affect the linter at all since the only things that have changed here are tests and fixtures. I'll look into it some more but also we could just revert this since it's just a refactor.

[p-linnane]

This is very much a best guess on my end for which recent PR changed this behavior. I don't think it's affecting enough stuff to revert, since that one instance is all I've seen having issues. If we can fix forward that'd be even better!

[apainintheneck]

It seems that there exists a handbrake cask as well and that's getting linted here for no reason. It'd probably be good to fix the test bot so that it only runs then audit on formulae here as well. But that doesn't really solve the root of the problem, just the symptom.