Testing — unit testing, integration testing, and test automation in Java
A comprehensive guide to JUnit 6 test naming conventions: the should-when pattern, BDD-style given-when-then, @DisplayName sentences, @DisplayNameGeneration strategies, custom generators, and a table of naming anti-patterns to avoid.
Learn how JUnit 6 Assumptions differ from Assertions, and how to use assumeTrue, assumeFalse, assumingThat, and conditional annotations like @EnabledOnOs, @EnabledOnJre, and @EnabledIfEnvironmentVariable to skip tests gracefully when preconditions are not met.
A complete reference guide to every JUnit 6 assertion method: assertEquals, assertThrows, assertAll, assertTimeout, assertIterableEquals, and more — each explained with real code examples, expected output, and when to use which.
A practical guide to writing clean, readable, and maintainable JUnit 6 tests. Covers the Arrange-Act-Assert pattern, one behaviour per test, @DisplayName, assertAll, avoiding logic in tests, and six habits that separate good tests from great ones.
A complete guide to the JUnit 6 test lifecycle: @BeforeAll, @BeforeEach, @AfterEach, @AfterAll. Includes execution order diagrams, PER_METHOD vs PER_CLASS lifecycle comparison, nested class behaviour, and real console output examples.
A deep dive into JUnit 6's three-pillar architecture: Platform, Jupiter, and Vintage. Learn how the TestEngine SPI, Launcher, and LauncherDiscoveryRequest work together, with code examples showing programmatic test execution and custom engine concepts.
A detailed, side-by-side comparison of JUnit 6 and JUnit 5 — architecture, annotations, parameterized tests, extension model, and records support — plus a practical migration guide updated for Spring Boot 4.0, which makes JUnit 6 the default testing baseline.
Learn how to structure your JUnit 6 test projects for scalability and long-term maintainability. Covers package layout, naming conventions, test base classes, test helpers, and real-world best practices used in production Java projects.
A comprehensive guide to configuring JUnit 6 with Maven and Gradle. Covers Surefire plugin, Failsafe plugin, multi-module projects, test filtering, IDE integration, and common configuration mistakes to avoid.
In modern microservices architecture, it's rare for a service to live in complete isolation. Most applications need to communicate with other services over the network, typically via REST APIs. When you build a component that consumes an external REST API, a critical question arises: how do you test it reliably without actually making network calls to a live, and potentially unstable, external service? This is where Spring Boot's test slices come to the rescue. For testing your REST clients, the framework provides a powerful and elegant solution: the @RestClientTest annotation. Let's dive deep into how you can use it to write clean, fast, and reliable tests for your HTTP client components. What Exactly is @RestClientTest? @RestClientTest is a "test slice" annotation specifically designed to test REST client components. Instead of loading your entire Spring application context (like @SpringBootTest does), it focuses only on the beans relevant to REST client operations. This makes your tests significantly faster and less prone to side effects from unrelated configurations. When you use @RestClientTest, Spring Boot will auto-configure the following for you: The Client Under Test: The specific REST client bean you want to test. MockRestServiceServer: A bean that lets you mock the server-side responses. You can instruct it: "When my client calls /api/employees/1, respond with this specific JSON." RestTemplateBuilder: Used to help construct RestTemplate instances. Jackson/Gson Support: It automatically includes support for serializing and deserializing JSON, so you can test your client-side data mapping. In short, it provides the perfect, minimal environment to verify that your client builds the correct HTTP request and correctly parses the HTTP response — all without a single packet leaving your machine.