add GitHub Action

.github/workflows/php.yml

@@ -0,0 +1,27 @@
+name: PHP Composer
+
+on: [ push, pull_request ]
+
+jobs:
+    test:
+        runs-on: ubuntu-latest
+        steps:
+            -   uses: actions/checkout@v2
+
+            -   name: Validate composer.json and composer.lock
+                run: composer validate --strict
+
+            -   name: Cache Composer packages
+                id: composer-cache
+                uses: actions/cache@v2
+                with:
+                    path: vendor
+                    key: ${{ runner.os }}-php-${{ hashFiles('**/composer.lock') }}
+                    restore-keys: |
+                        ${{ runner.os }}-php-
+
+            -   name: Install dependencies
+                run: composer install --prefer-dist --no-progress
+
+            -   name: Unit tests
+                run: composer run test

composer.json

@@ -18,6 +18,9 @@
     "require-dev": {
         "phpunit/phpunit": "^9.5"
     },
+    "scripts": {
+        "test": "vendor/bin/phpunit"
+    },
     "license": "MIT",
     "authors": [
         {