Testing Your Changes

We saw the basics of testing in Android back in a previous chapter. However, that was just with some pre-defined tests created by Android Studio’s new-project wizard.

Presumably, your app will have more code that needs testing.

(if your app is purely the result of the new-project wizard templates, feel free to skip this chapter)

In this chapter, we will explore a bit more about how to write and run tests in Android, so that you can test your app code.

A Quick Recap

There are two broad categories of tests in Android: instrumented tests and unit tests.

Instrumented tests:

Run in Android, on a device or emulator
Have full access to the Android SDK, so you can test most of your app
Run relatively slowly

Unit tests:

Run outside of Android, directly on your development machine or CI server, in whatever operating system that is running (Windows, macOS, Linux)
Have no access to the actual Android SDK, so your testing will tend to be focused on pure-Java/Kotlin code
Run relatively quickly

Both categories of tests will look the same on the surface, in that both use JUnit4 and have similar structures (e.g., @Test-annotated methods or functions).