java-spring-boot-testing

name	java-spring-boot-testing
description	Complete guide to testing in Spring Boot — unit tests with Mockito, controller tests (MockMVC standalone, @WebMvcTest, MockMvcTester, @SpringBootTest, WebTestClient), JPA repository tests, Testcontainers, Spring Cloud Contract, and stress testing. Use when writing or reviewing any Spring Boot test.
metadata	{"scope":"testing","version":"1.0.0"}

Spring Boot Testing

Guide to testing strategies and examples for Spring Boot applications.

When to Use This Skill

• Write unit tests for services and components (JUnit 5 + Mockito)
• Write controller tests: unit (standalone MockMVC) or integration (@WebMvcTest, @SpringBootTest)
• Test JPA repositories with @DataJpaTest
• Use Testcontainers for real database integration tests
• Implement Consumer Driven Contracts with Spring Cloud Contract
• Diagnose or simulate thread pool starvation
• Benchmark performance with JMH

Reference Guide

Topic	Reference	Load When
Controller Tests	references/controller-tests.md	MockMVC standalone, @WebMvcTest, MockMvcTester, @SpringBootTest + MockMvc/TestRestTemplate, WebFluxTest + WebTestClient
Unit Testing	references/unit-testing.md	Service/component tests with Mockito, parameterized tests, test data builders
JPA Tests	references/data-jpa-test.md	@DataJpaTest, TestEntityManager, H2, real database, rollback, ordered tests
Testcontainers	references/testcontainers.md	PostgreSQL container, DynamicPropertySource, AbstractIntegrationTest
Test Configuration	references/test-configuration.md	application-test.yml, @TestConfiguration, TestDataFactory
Contract Testing	references/contract-testing.md	Spring Cloud Contract, Consumer Driven Contracts, WireMock stubs
Stress Testing	references/stress-testing.md	Thread pool starvation with JMeter, JMH micro-benchmarks

Testing Best Practices

• Follow the AAA pattern (Arrange, Act, Assert)
• Use @DisplayName for descriptive test names
• Mock external dependencies in unit tests; use Testcontainers for real DB
• Achieve 85%+ code coverage
• Test both happy path and edge/error cases
• Use @Transactional for automatic test data cleanup
• Keep unit tests and integration tests in separate source sets or naming conventions
• Use parameterized tests to cover multiple input scenarios
• Test security rules (@WithMockUser) and input validation
• Keep tests fast and independent — avoid shared mutable state