Add basic test setup

Author: esdoefom

composer.json

@@ -24,7 +24,8 @@
       "ext-intl": "*"
     },
     "require-dev": {
-        "phpunit/phpunit": "^10.2"
+        "phpunit/phpunit": "^10.2",
+        "orchestra/testbench": "^8.5"
     },
     "config": {
         "allow-plugins": {