Testing Kotlin Applications: From Unit to E2E

Modern Kotlin development is impossible without quality testing. The book "Testing Kotlin Applications" is a comprehensive guide that will take you from the basics of unit testing to complex integration and end-to-end testing scenarios. Whether you are writing Android applications or backend services on Spring Boot, this book will become your desktop reference.

What is this book about?

The author systematically covers all stages of testing Kotlin projects:

• Unit Testing Basics — setting up JUnit 5, Kotest and Spek, writing clean and isolated tests.
• Mocking and Stubs — deep dive into MockK: creating mocks, verifying calls, working with lambdas and extension functions.
• Testing Coroutines and Flow — how to properly test asynchronous code, use TestCoroutineDispatcher and verify data streams.
• Integration Tests — testing with real databases (Exposed, Room), REST APIs (Ktor, Retrofit) and external services.
• Testing Android Components — Activity, ViewModel, Compose UI: Robolectric, Espresso and Compose Test.
• Property-based Testing — generating random data with kotlinx.kotest-property and verifying invariants.
• CI/CD and Reporting — integrating tests into GitHub Actions, generating Allure reports, code coverage metrics.

Who is this book for?

• Android and Kotlin backend developers who want to write reliable tests.
• Teams migrating from Java to Kotlin — the book will help master language-specific tools.
• Team leads and architects interested in implementing a testing culture.
• Junior and Middle developers looking to deepen their knowledge of TDD and BDD.

What will you learn?

• How to set up a test environment for a Kotlin project of any complexity.
• Why MockK is more convenient than Mockito for Kotlin and how to avoid common mistakes.
• How to test coroutines and channels without flaky tests.
• Principles of testing Compose interfaces and ViewModel.
• How to organize test infrastructure for a microservice architecture.

Each chapter contains practical examples ready for use in real projects. The code is available on GitHub and accompanied by detailed comments. The book is written in a lively style, without excessive academicism, and is suitable both for self-study and for team code reviews.

Make your Kotlin applications stable, predictable, and ready for any changes. Add "Testing Kotlin Applications" to your library today!