Unit testing is essential to expediting your development time and minimizing regression issues that reach QA or even production. In this article, we'll examine how to utilize Mockito, Robolectric to expedite various aspects of unit testing. Outside of unit tests it's important to also test the UI to assert current state after a sequence of simulated user gestures or input utilizing Espresso. Finally, we'll cover how to maximize our code reuse for our Espresso tests by adhering to Jake Wharton's Robot Pattern.