Setting up and writing tests

As a software developer, you probably enjoy writing code. Seeing an app gain functionality feels very rewarding, probably more than writing tests—or worse, finding bugs—yet testing and debugging are essential. Eventually, your code will contain bugs, because all non-trivial programs do. To make your developer life easier, you need to familiarize yourself with writing tests and debugging your own and others’ code. Testing an app has various facets that correspond to different types of tests, as outlined here:

• Unit test: You need to make sure that the business logic works as expected. This, for example, means that formulas and calculations always produce correct results.
• Integration tests: Are all building blocks of the app properly integrated? Depending on what the app does, this may include accessing remote services, talking to a database, or reading and writing files on the device.
• UI tests: Is the UI accurate? Are...