Minor test adjustments

[Firehed]

• Updates gitignored directory for PHPUnit updates
• Finds test vector files relative to the test file's location

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.41%. Comparing base (fa24407) to head (f0eaaa0).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main      #94   +/-   ##
=========================================
  Coverage     81.41%   81.41%           
  Complexity      335      335           
=========================================
  Files            33       33           
  Lines          1033     1033           
=========================================
  Hits            841      841           
  Misses          192      192           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.