In Chapter 7, Testing, Debugging, and Deploying Twilio Apps, we looked at using flow charts to better plan and test our applications. Of course, you can draw these on paper, but as all developers know, a computer is always the best way!

I recommend Draw.io (https://www.draw.io), which is free and browser-based, but tools such as Gliffy (http://www.gliffy.com), Lucidchart (https://www.lucidchart.com), and the ever-popular (if expensive) OmniGraffle (https://www.omnigroup.com/omnigraffle) are great choices too.