App Inventor provides one great tool for testing and debugging: Do It. You can right-click on any block at any time, as long as a device or emulator is connected, and select Do It from the menu. This option runs that block immediately on the device, even if it is not inside an event (see Figure 8.7).
The Do It feature is simple, and you can use it in many ways, depending on what blocks you have and what you need to test. Here are some examples of how you can use Do It to help with testing and debugging:
Reset lists (set a list to an empty list)
Move sprites to start locations ...