I have built an action with Actions-on-Google(2.5.0) and dialogflow-fulfillment(0.6.1) Node.js Library. I cannot test my app on dialogflow test console because I return conv object which is not supported there. Now, I cannot test it in the google action simulator, either. This is the error I get:
Invocation Error You cannot use standard Google Assistant features in the Simulator. If you want to try them, use Google Assistant on your phone or other compatible devices.
I'd like to use the simulator, so I can debug better.
It is how the error message says: The simulator lacks many features that normal Assistant surfaces (speaker, Assistant app) have and can even sometimes give you completely wrong error messages. There is really no way around testing your app on real devices.
You can however view the same logs that you see in the simulator in Google Stackdriver Logging. To activate this go to the settings of your Dialogflow agent, select the "General" tab and activate the "Log interactions to Google Cloud" option. Then click on the link below the button to get to the logs. The default view will probably show you only the Actions-on-Google logs, i.e. the requests between your users and AoG. To see the requests between Dialogflow and your webhook click on the dropdown arrow in the filter box, select "Convert to advanced filter" and set the filter to resource.type="global".