tests: improve plugin option merge test

[hukkin]

No description provided.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (e3b4c33) to head (1ffb6e7).
Report is 21 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##            master      #499   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           15        15           
  Lines          947       947           
  Branches       166       166           
=========================================
  Hits           947       947           

☔ 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.