Fix tests timing

tests/validation/config.json

@@ -4,7 +4,8 @@
         {
             "title": "Node material #1",
             "playgroundId": "#QJ71C6#0",
-            "referenceImage": "node-material1.png"
+            "referenceImage": "node-material1.png",
+            "renderCount": 20
         },     
         {
             "title": "Node material #2",