Local vs. on-device

- [Female] The Android operating system is spelled…using the Java programming language.…When you write an Android app, you are using…the Java core functionality with additional code…provided by the Android operating system.…Java is a widely used language,…and the Java part of your app can be executed…on any machine that runs a Java Virtual Machine, the JVM.…This includes your computer,…whether the is a desktop or a laptop.…

However, to run and therefore test an Android app,…you will need an Android device,…either a physical one or an emulator.…In either case, when you run your test,…you will need to transfer your app…and test code from the host computer to the device…and install it.…This takes time,…therefore, it is genuinely desirable to organize your code…such that you can compartmentalize the Java code,…the part without any Android libraries…into separate modules,…and test them with JVM unit tests.…

That is the fastest kind of test you can run,…and it's a great way to test business logic code.…But because the JVM does not have any knowledge…