Ensuer "lowest" tests correct versions

.github/workflows/tests.yaml

@@ -4,7 +4,6 @@ on:
   push:
     branches: [ "main" ]
   pull_request:
-    branches: [ "main" ]
 
 permissions:
   contents: read
@@ -56,15 +55,22 @@ jobs:
         uses: shivammathur/setup-php@v2
         with:
           php-version: ${{ matrix.php-version }}
+          ini-file: development
 
       - name: Install dependencies
         uses: ramsey/composer-install@v3
         with:
           dependency-versions: ${{ matrix.dependencies }}
 
+      - name: Validate lowest dependencies
+        if: matrix.dependencies == 'lowest'
+        run: |
+          composer require --dev dereuromark/composer-prefer-lowest --no-interaction
+          vendor/bin/validate-prefer-lowest
+
       - name: Add Pimcore Admin UI
-        run: composer require --dev pimcore/admin-ui-classic-bundle --no-interaction
         if: matrix.dependencies == 'highest'
+        run: composer require --dev pimcore/admin-ui-classic-bundle --no-interaction
 
       - name: Execute tests
         run: composer tests -- ${{ matrix.phpunit-flags }}