NGSTACK-816 add testing workflow

.github/workflows/tests.yaml

@@ -0,0 +1,33 @@
+name: Tests
+
+on:
+  push:
+    branches:
+      - 'master'
+      - '[0-9].[0-9]+'
+  pull_request: ~
+
+jobs:
+  tests:
+    name: ${{ matrix.php }} / ${{ matrix.phpunit }}
+    runs-on: ubuntu-latest
+
+    strategy:
+      fail-fast: false
+      matrix:
+        php: ['8.1']
+        phpunit: ['phpunit.xml']
+
+    steps:
+      - uses: actions/checkout@v2
+      - uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php }}
+          coverage: none
+
+      - run: composer --version
+      - run: composer validate --strict
+
+      - run: composer update --prefer-dist
+
+      - run: vendor/bin/phpunit -c ${{ matrix.phpunit }} --colors=always