During the design phase of your project, you will want to test your app periodically to check for bugs and see how it looks and behaves from a user's perspective. You can do this at any time by selecting one of the Web Browser icon buttons on the button bar. When running in test mode, you will be able to preview page transition effects, sounds, dialog boxes and see how buttons and other interactive objects behave – just as a user would see them. This provides you with the opportunity to find mistakes and make any necessary adjustments before sharing your app with the world.
Those buttons will lauch your app in a web browser. The web browser provides a way to quickly preview and test apps. Any modern web browser includes a Debugger tool (Press F12 to open it while testing your app) that allows you to monitor any possible error and watch Consolelog printed strings. The web browser also allows you to temporarily change the app's size and orientation so you can see how it will look on different devices with different screen dimentions. Refer to your selected web browser help documentation to know more about this.
You can test your app any browsers like Chrome, Firefox, Opera, Edge and neoEdge - provided you have them installed on your PC. It always a good idea to test your apps on any browsers, platforms and devices where it is likely to be used. Browsers, phones and tablets often have different capabilities and quirks.
If you don't see other browsers listed under the 'Run in Web Browser' menu, you will need to go to the browser publisher's website and download the appropriate software. For example, the Chrome browser can be download from Google's website here.