Update PHPUnit version

ben221199 · ben221199 · commit e2ecf38502c9 · 2021-04-11T16:19:58.000+02:00
diff --git a/composer.json b/composer.json
@@ -15,7 +15,7 @@
         "php": "^5.6 || ^7.0"
     },
     "require-dev": {
-        "phpunit/phpunit": "^5.7 || 6.3.*"
+        "phpunit/phpunit": "^5 || ^6 || ^7 || ^8 || ^9"
     },
     "autoload": {
         "psr-4": {
