JUnit is a unit testing framework for the Java programming language.
Instrumented unit tests are tests that run on physical devices and emulators, and they can take advantage of the Android framework APIs and supporting APIs, such as the Android Testing Support Library. You should create instrumented unit tests if your tests need access to instrumentation information (such as the target app's Context) or if they require the real implementation of an Android framework component (such as a Parcelable or SharedPreferences object).
Lint can help you to identify and correct problems with the structural quality of your code without your having to execute the app or write test cases