Testing Kotlin Applications: From Unit Tests to E2E

Modern development in Kotlin requires not only knowledge of syntax, but also the ability to create reliable, easily maintainable software. The book "Testing Kotlin Applications" is a comprehensive guide that will help you master all aspects of testing code in Kotlin: from simple unit tests to complex end-to-end scenarios.

What this book is about

The author consistently guides the reader through the entire process of ensuring code quality. You will learn how to:

• Set up a test environment using JUnit5, Spek, and Kotest
• Write isolated unit tests using the MockK library for mocking dependencies
• Test coroutines and Flow — key asynchronous constructs for Kotlin
• Conduct integration testing with real databases (Exposed, Room) and HTTP clients (Ktor Client, Retrofit)
• Implement UI testing on Android and server applications (Spring Boot, Ktor)
• Apply TDD (Test-Driven Development) practices in daily work
• Automate test execution in CI/CD pipelines (GitHub Actions, TeamCity)

Who this book is for

This book will be useful for:

• Junior and Middle developers who want to systematize their knowledge of testing
• Android developers striving to write stable applications with a minimum number of bugs
• Backend developers using Kotlin who need tools for testing REST APIs and business logic
• Team Leads and architects implementing a culture of quality in their team

What you will gain after reading

• Confident mastery of all popular testing frameworks for Kotlin
• Ability to design testable code from scratch
• Skills for writing fast, stable, and informative tests
• Ready-made templates for testing typical scenarios (databases, APIs, UI)
• Understanding of code coverage metrics and how to interpret them

The book contains many practical examples that can be immediately applied in real projects. All examples are available for download and come with detailed comments. Whether you are working on a mobile application, a microservice, or a library — this guide will become your reliable companion in the world of Kotlin testing.

Note: The book assumes a basic knowledge of the Kotlin language and general development principles. No prior experience in testing is required to study it — all concepts are explained from scratch.