The Monkey is a program that runs on your emulator or device and generates pseudo-random streams of user events such as clicks, touches, or gestures, as well as a number of system-level events. You can use the Monkey to stress-test applications that you are developing, in a random yet repeatable manner.
read details in Android document - UI/Application Exerciser Monkey
Example to run "adb shell monkey ...", to test my example.