Add job with PHPUnit 12 to CI

Author: kubawerlos

.github/workflows/ci.yaml

@@ -75,6 +75,10 @@ jobs:
             description: 'on Windows'
             php-version: '8.4'
             FAST_LINT_TEST_CASES: 1
+          - os: ubuntu-latest
+            description: 'with PHPUnit 12'
+            php-version: '8.4'
+            install-phpunit-12: true
           - os: ubuntu-latest
             php-version: '8.5'
     runs-on: ${{ matrix.os }}
@@ -116,6 +120,11 @@ jobs:
       - if: ${{ matrix.calculate-coverage }}
         run: composer require --dev php-coveralls/php-coveralls --no-update
 
+      - if: matrix.install-phpunit-12
+        run: |
+          composer require --dev --with-all-dependencies friendsofphp/php-cs-fixer:dev-master phpunit/phpunit:^12.0.2
+          php php-cs-fixer fix --quiet --rules=php_unit_attributes
+
       - run: composer update --no-progress --classmap-authoritative ${{ matrix.composer-flags }}
 
       - run: composer show | grep php-cs-fixer