[FEATURE] Test with Symfony 6 on CI (#1109)

We will be able to remove the additional CI job once
a stable version of Symfony 6 has been released.

Fixes #1101

.github/workflows/ci.yml

@@ -184,3 +184,45 @@ jobs:
 
       - name: Run Tests
         run: composer ci:tests:unit
+
+  unit-tests-symfony-6:
+    name: Unit tests with Symfony 6
+
+    runs-on: ubuntu-20.04
+
+    needs: [ php-lint, composer-validate ]
+
+    strategy:
+      matrix:
+        php-version:
+          - 8.0
+          - 8.1
+        dependencies:
+          - lowest
+          - highest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Install PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php-version }}
+          ini-values: xdebug.max_nesting_level=500
+          tools: composer:v2
+          coverage: none
+
+      - name: Install Composer dependencies
+        run: |
+          if [[ "${{ matrix.dependencies }}" == 'lowest' ]]; then
+            DEPENDENCIES='--prefer-lowest';
+          else
+            DEPENDENCIES='';
+          fi;
+          composer require symfony/css-selector:^6.0.x-dev --no-progress
+          composer update --with-dependencies --no-progress "${DEPENDENCIES}";
+          composer show;
+
+      - name: Run Tests
+        run: composer ci:tests:unit

CHANGELOG.md

@@ -6,6 +6,7 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 ## x.y.z
 
 ### Added
+- Test with Symfony 6-dev (#1109)
 - Add support for PHP 8.1 (#1103)
 - Add a dedicated class for caching (#1097)
 - Allow installation together with Symfony 6 (#1065)