Testing coroutine-based code in Kotlin can be challenging due to its asynchronous nature. Fortunately, Kotlin’s kotlinx.coroutines library provides helpful utilities for testing, including the runTest function. Let’s dive into how to effectively use runTest and streamline coroutine testing in your Kotlin projects. runTest You’re probably used runTest before. Let me quote kotlinlang.org: Executes testBody as a test in a new coroutine, returning TestResult. On JVM and Native, this function behaves similarly to runBlocking, with the difference that the code that it runs will skip delays.

Imagine you have a suspend function like this: 1 2 3 suspend fun doSomething() = withContext(Dispatchers.IO) { // body } This looks alright. Using withContext every time looks a bit verbose though. There’s a nifty Kotlin extension on the invoke function that simplifies the code and makes it cleaner. 1 2 3 4 5 import kotlinx.coroutines.invoke suspend fun doSomething() = Dispatchers.IO { // body } The invoke extension allows you to specify the dispatcher directly within the function call, eliminating the need for withContext.