Testing Java Applications: From Unit Tests to Integration Scenarios

The book "Testing Java Applications" is a practical guide that will help Java developers of any level master the art of writing reliable and effective tests. In modern development, code quality directly affects release speed and product stability, and automated testing is becoming a mandatory skill, not an option.

The author, Alexey Smirnov, a senior developer with 10 years of experience, consistently guides the reader from the basics of unit testing to complex integration scenarios. The book is built on the "from simple to complex" principle and contains many real-world examples from commercial development.

What you will learn:

• How to properly write unit tests using JUnit 5 and TestNG
• Creating mock objects with Mockito and PowerMock to isolate the code under test
• Testing databases with H2, Testcontainers, and Spring Data JPA
• Integration testing of REST API with Spring Boot Test and MockMvc
• Automating UI tests with Selenium WebDriver and Page Object Model
• Parameterized tests, exception testing, and multithreading
• Best practices: test structure, naming, code coverage, and CI/CD
• Working with reports: Allure, JaCoCo, SonarQube

Who this book is for:

• Junior and Middle Java developers who want to improve the quality of their code
• Team Leads and architects implementing a testing culture in their team
• QA engineers transitioning to test automation
• Students and course graduates preparing for technical interviews

Each chapter contains not only theory but also ready-made code examples that can be immediately applied in a project. At the end of the book, you will find a checklist for auditing test coverage and templates for setting up CI pipelines with GitHub Actions and Jenkins.

After reading, you will be able to confidently design test architecture, avoid common mistakes, and achieve stable product quality. The book will become a desktop reference for any Java developer striving for professional growth.