Add code style enforcement and GitHub Actions workflow for tests (#3)

* Add PHP_CodeSniffer and fix code style

* Add test pipeline and SonarQube analysis

* Fix job name of workflow

.github/workflows/tests.yml

@@ -0,0 +1,61 @@
+name: Tests
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+    types: [opened, synchronize, reopened]
+
+jobs:
+  test-all:
+    name: Test PHP ${{ matrix.php-version }}
+
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        php-version: ['7.4', '8.0']
+
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+
+      - name: Setup PHP ${{ matrix.php-version }}
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php-version }}
+          tools: phpunit:9.5.0
+          coverage: pcov
+
+      - name: Setup problem matchers for PHP
+        run: echo "::add-matcher::${{ runner.tool_cache }}/php.json"
+
+      - name: Setup problem matchers for PHPUnit
+        run: echo "::add-matcher::${{ runner.tool_cache }}/phpunit.json"
+
+      - name: Get Composer Cache Directory
+        id: composer-cache
+        run: |
+          echo "::set-output name=dir::$(composer config cache-files-dir)"
+
+      - name: Cache Composer dependencies
+        uses: actions/cache@v2
+        with:
+          path: ${{ steps.composer-cache.outputs.dir }}
+          key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.lock') }}
+          restore-keys: ${{ runner.os }}-composer-
+
+      - name: Install composer dependencies
+        run: composer install --prefer-dist --ignore-platform-reqs
+
+      - name: Run tests
+        run: composer test
+
+      - name: Run SonarQube analysis
+        uses: sonarsource/sonarcloud-github-action@master
+        if: matrix.php-version == '8.0'
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          SONAR_TOKEN: ${{ secrets.SONARCLOUD_TOKEN }}