Test with multiple versions of the dependencies

.github/workflows/push.yml

@@ -56,6 +56,10 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
+        dependencies:
+          - highest
+          - locked
+          - lowest
         operating-system:
           - ubuntu-latest
           - windows-latest
@@ -105,10 +109,11 @@ jobs:
           GITHUB_AUTH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         run: phive --no-progress install --copy --trust-gpg-keys ${{ env.phiveGPGKeys }} phpunit:^8.5
 
-      - name: Install Composer dependencies & cache dependencies
+      - name: Install Composer ${{ matrix.dependencies }} dependencies & cache dependencies
         uses: "ramsey/composer-install@v1"
         with:
           composer-options: --optimize-autoloader
+          dependency-versions: ${{ matrix.dependencies }}
 
       - name: Run PHPUnit
         run: php tools/phpunit