Ensure XDEBUG is running for test coverage

Author: maennchen

.github/workflows/part_test.yml

@@ -66,6 +66,8 @@ jobs:
         run: composer install --prefer-dist --ignore-platform-req=php+
       - name: Run PHPUnit
         run: composer run test:unit
+        env:
+          XDEBUG_MODE: coverage
       - name: Upload coverage results to Coveralls
         env:
           COVERALLS_REPO_TOKEN: ${{ secrets.GITHUB_TOKEN }}