We are software developers, and we develop some applications. In this particular case, we develop mobile applications. The code that we write could be put in the browser, as a mobile program, or started as a Node.js script. In different cases, we expect particular results. Every line of code means something, and we need to know that the final product is doing what we need. Normally, we debug our applications. For example, we write part of the application and run it. We use different debugging tools and approaches. Sometimes, we use more complex tools, such as GapDebug, or something simple, such as visual acceptance or console.log. By monitoring the output or looking at the way it behaves, we know whether everything is good or there is a problem. However, this approach takes time, especially if the project is big and growing. Iterating over and over again through every single feature of the application could cost a lot of time and money. Automatic testing could help in such...