A Rule is a way to run code before and after the execution of a test in JUnit.

Different kinds of rules ​

• InstantTaskExecutorRule is a JUnit rule that configures LiveData to execute each task synchronously
• MainCoroutineScopeRule is a custom rule in this codebase that configures Dispatchers.Main to use a TestCoroutineDispatcher from kotlinx-coroutines-test. This allows tests to advance a virtual-clock for testing, and allows code to use Dispatchers.Main in unit tests. The MainCoroutineScopeRule lets you pause, resume, or control the execution of coroutines that are launched on the Dispatchers.Main.