Run PHPUnit as GitHub Actions workflow

Author: mpdude

.github/workflows/lock-symfony-version.sh

@@ -0,0 +1,3 @@
+#!/bin/sh
+
+sed --in-place --regexp-extended --expression='s/"(symfony\/.*)": "\^.*"/"\1": "'$VERSION'"/' composer.json

.github/workflows/tests.yml

@@ -0,0 +1,43 @@
+name: Tests
+
+on:
+    push:
+        branches:
+            - master
+    pull_request:
+
+env:
+    SYMFONY_DEPRECATIONS_HELPER: weak
+    PHP_VERSION: 7.2
+
+jobs:
+    PHPUnit:
+
+        runs-on: ubuntu-20.04
+        strategy:
+            fail-fast: false
+            matrix:
+                include:
+                    - { symfony-locked-version: none, dependency-version: prefer-lowest }
+                    - { symfony-locked-version: 3.4.*, dependency-version: prefer-stable }
+                    - { symfony-locked-version: 4.4.*, dependency-version: prefer-stable }
+        name: PHPUnit (Symfony Version Lock ${{ matrix.symfony-locked-version }}, ${{ matrix.dependency-version }})
+        steps:
+            -   uses: actions/checkout@v2
+            -   uses: shivammathur/setup-php@v2
+                with:
+                  php-version: ${{ env.PHP_VERSION }}
+                  tools: composer:v2
+            -   uses: actions/cache@v2
+                with:
+                    path: vendor
+                    key: composer-${{ runner.os }}-${{ env.PHP_VERSION }}-${{ matrix.symfony-locked-version }}-${{ matrix.dependency-version }}-${{ hashFiles('composer.json', 'composer.lock') }}
+                    restore-keys: |
+                        composer-${{ runner.os }}-${{ env.PHP_VERSION }}-${{ matrix.symfony-locked-version }}-${{ matrix.dependency-version }}-
+                        composer-${{ runner.os }}-${{ env.PHP_VERSION }}-
+                        composer-${{ runner.os }}-
+            -   run: VERSION=${{ matrix.symfony-locked-version }} .github/workflows/lock-symfony-version.sh
+                if: matrix.symfony-locked-version != 'none'
+            -   run: composer update --${{ matrix.dependency-version }} --no-interaction --no-scripts --no-progress --prefer-dist
+            -   run: composer show
+            -   run: vendor/bin/phpunit