[fix] support L5.8 and 6.0

Author: adammatysiak

composer.json

@@ -16,7 +16,7 @@
     },
     "require-dev": {
         "phpunit/phpunit": "6.*|7.*|8.*",
-        "orchestra/testbench" : "4.*",
+        "orchestra/testbench" : "3.*|4.*",
         "mockery/mockery": "^1.0"
     },
     "autoload": {