The Conversation Simulator is the quickest way to test out different conversational flows based on your designs.
It puts you in the driving seat and shows you what flows are possible given a certain utterance from either the user or the application. It is focused on flow and does not take into account interpretation or any conditions, which means you can explore all possible paths quickly.
To start it click on the play button within the action bar.
It allows you to choose an intent that the user could express to get the conversation started.
As you can see from the image above the user can have multiple choices and after you've picked one you get the example message associated with that intent in the chat window.
This allows you to quickly try out ideas and also show them to potential stakeholders to confirm expectations, before diving into actually setting up NLU or doing detailed messaging.