Run tests on PHP 8

Author: mnapoli

.github/workflows/ci.yml

@@ -16,7 +16,7 @@ jobs:
         timeout-minutes: 15
         strategy:
             matrix:
-                php: [ '7.2', '7.3', '7.4' ]
+                php: [ '7.2', '7.3', '7.4', '8.0' ]
                 dependency-version: [ '' ]
                 include:
                     -   php: '7.2'
@@ -51,7 +51,7 @@ jobs:
                 uses: shivammathur/setup-php@v2
                 with:
                     php-version: 7.4
-                    tools: composer, cs2pr
+                    tools: composer:v2, cs2pr
                     coverage: none
             -   name: Cache Composer dependencies
                 uses: actions/cache@v2

composer.json

@@ -18,7 +18,7 @@
         "php": ">=7.2.0"
     },
     "require-dev": {
-        "phpunit/phpunit": "~8.5",
+        "phpunit/phpunit": "^8.5|^9.0",
         "mnapoli/hard-mode": "~0.3.0"
     }
 }