bugfix(tests): unit

composer.json

@@ -13,7 +13,7 @@
         "wpdesk/wp-plugin-flow-common": "^1"
     },
     "require-dev": {
-        "phpunit/phpunit": "<7",
+        "phpunit/phpunit": "^7||^8||^9",
         "wp-coding-standards/wpcs": "^0.14.1",
         "squizlabs/php_codesniffer": "^3.0.2",
         "mockery/mockery": "*",