Testing Java Applications: From Unit Tests to Integration Checks

The book "Testing Java Applications" is a practical guide that will help you master all aspects of automated testing in the Java ecosystem. From the basics of writing simple unit tests to complex integration and E2E scenarios, the author consistently guides the reader through all stages of creating high-quality test coverage.

Who this book is for:

• Java developers of any level who want to implement TDD (Test-Driven Development) in their work
• QA engineers transitioning to test automation in Java
• Team leads and architects responsible for code quality in a project
• Students and novice programmers learning professional development

What you will learn:

• Basics of JUnit 5: annotations, assertions, test lifecycle
• Working with mocks and stubs using Mockito and EasyMock
• Database testing: H2, Testcontainers, embedded databases
• Integration testing of Spring Boot applications (Spring Test, @WebMvcTest, @DataJpaTest)
• UI testing with Selenium WebDriver and Playwright
• Load testing: JMeter and Gatling for Java services
• CI/CD test integration: GitHub Actions, Jenkins, Maven/Failsafe plugins
• Test design patterns: Page Object, Test Data Builder, Fluent Assertions

Each chapter contains real code examples that can be immediately applied in a project. The book is written in accessible language, without excessive theory — only what is needed in practice. You will learn to write maintainable and stable tests that will become a reliable foundation for your application.

Special attention is given to common mistakes and anti-patterns in testing. The author shares experience on how to avoid brittle tests, make them fast and informative. You will learn how to properly organize test infrastructure in a large project and which quality metrics truly matter.

The book is suitable both for self-study and for corporate training. After reading it, you will be able to confidently cover code of any complexity with tests and implement a culture of quality in your team.