Creator here. As a VUI designer, I have struggled with understanding how people will talk to my app. To understand it better I was meeting with users and was asking them to talk to my app. They thought the app was launched in production, but it was just me playing texts out loud using just Google Translate.

So my team and I built Tortu. Workflow is simple: you map out the conversation using flowchart and then test it with the in-browser prototype. The flowchart has only two types of blocks: "user says", "system says". The prototype has voice, text and "chat bubbles" modes.

We learned a lot while coding since we have never worked with flowcharts before. We use GoJS for building interactive diagrams. We were considering D3 but GoJS is built especially for diagrams and has features working out of the box such as "undo/redo", "copy/paste", "drag and drop".

For text to speech, we use Google Text To Speech and Amazon Polly. And for speech recognition, we use Google Speech. The frontend code is in Typescript (React), the backend is in Python (Django).

The tool is free and will stay free forever if you sign up while it is in beta.

Happy to answer any of your questions!