Summary - Advanced testing

Combine runTest, Turbine and MockK to write a ViewModel test.

Summary - Advanced testing

In this group you saw the advanced testing tools: runTest for coroutines, Turbine for Flows, MockK for mocking, Testcontainers for real containers and kotest-property for property tests.

This lesson includes a small task that combines three of them: you will write a test that calls fetchUser inside runTest and prints the result. This pattern is the foundation of advanced Kotlin testing.

Exercise Summary: write the fetchUser test

Define a suspend function fetchUser(id: Int): String that returns "Alex" when id is 1. In main open a runTest block; assign the result of fetchUser(1) to a variable, assert it with assertEquals("Alex", result) and print println(result).

Show example solution

import kotlinx.coroutines.test.runTest
import kotlin.test.assertEquals

suspend fun fetchUser(id: Int): String {
    return "Alex"
}

fun main() = runTest {
    val result = fetchUser(1)
    assertEquals("Alex", result)
    println(result)
}

Test yourself

Which builder is used to test a suspend function?
- Thread.sleep
- runBlocking
- runTest
- Thread.start
Show answer

runTest — runTest opens a TestScope for suspend functions.

Complete the Turbine test block

scoreFlow().____ {
    println(awaitItem())
    awaitComplete()
}

Show answer

scoreFlow().test {
    println(awaitItem())
    awaitComplete()
}

Match the testing tools

runTest

Coroutine test
Turbine

Flow test
MockK

Mocking
kotest-property

Property test

Next lesson: Immutability

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