added unit tests

.github/workflows/phpunit.yml

@@ -0,0 +1,27 @@
+name: PHPUnit
+
+on:
+  push:
+    branches: [main, master]
+  pull_request:
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: '8.2'
+          extensions: json, openssl, pdo, pdo_sqlite, zip
+          coverage: pcov
+          tools: composer:v2
+
+      - name: Install dependencies
+        run: composer install --no-interaction --prefer-dist
+
+      - name: Run tests with coverage floor
+        run: php tests/check-coverage.php 40