#1259 Make unit tests to run on PHP 7.2

tests/composer.json

@@ -1,8 +1,8 @@
 {
     "name": "UNA.IO/UNA Tests",
     "require-dev": {
-        "phpunit/phpunit": "3.7.*",
+        "phpunit/phpunit": "6.*",
         "sebastian/phpcpd": "*",
-        "phpmd/phpmd": "1.4.*"
+        "phpmd/phpmd": "@stable"
     }
 }