feature: require passing phpunit tests on pull request

.github/workflows/phpunit.yml

@@ -0,0 +1,25 @@
+name: PHPUnit Tests
+
+on:
+  pull_request:
+    branches:
+      - develop
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+
+      - name: Set up PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: '8.1'
+
+      - name: Install dependencies
+        run: composer install
+
+      - name: Run PHPUnit tests
+        run: vendor/bin/phpunit