Add Test workflow

Author: Seif Kamal

.github/workflows/test.yml

@@ -0,0 +1,26 @@
+name: Test
+on: [push, pull_request]
+jobs:
+  test:
+    strategy:
+      matrix:
+        php-versions: ['7.0', '7.1', '7.2', '7.3', '7.4']
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php-versions }}
+      - name: Get composer cache directory
+        id: composer-cache
+        run: echo "::set-output name=dir::$(composer config cache-files-dir)"
+      - name: Cache dependencies
+        uses: actions/cache@v1
+        with:
+          path: ${{ steps.composer-cache.outputs.dir }}
+          key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.lock') }}
+          restore-keys: ${{ runner.os }}-composer-
+      - name: Install dependencies
+        run: composer install --no-progress --no-suggest --prefer-dist --optimize-autoloader
+      - name: Run tests
+        run: composer test

README.md

@@ -1,3 +1,4 @@
+![](https://github.com/safe-k/struct-array/workflows/Test/badge.svg)
 ![GitHub license](https://img.shields.io/github/license/safe-k/struct-array)
 
 # PHP Structured Arrays

composer.json

@@ -21,7 +21,7 @@
     "php": ">=7.0.0"
   },
   "require-dev": {
-    "phpunit/phpunit": "^9.1"
+    "phpunit/phpunit": "^6.0"
   },
   "autoload": {
     "psr-4": {