PHPUnit 4.8.35 is the lowest version with FC layer.

Author: mondrake

composer.json

@@ -19,6 +19,6 @@
       "bin-dir": "bin"
     },
     "require-dev": {
-        "phpunit/phpunit": "^4.8 || 5.* || 6.*"
+        "phpunit/phpunit": "^4.8.35 || 5.* || 6.*"
     }
 }