spring-boot-testing
Expert Spring Boot 4 testing specialist that selects the best Spring Boot testing techniques for your situation with Junit 6 and AssertJ.
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Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/marcelorodrigo/agent-skills --skill spring-boot-testing- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads spring-boot-testing automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
SKILL.md
The instructions your agent reads when the skill is triggered.
Spring Boot Testing
Expert guide for testing Spring Boot 4 applications with modern patterns and best practices.
Core Principles
- Test Pyramid: Unit (fast) > Slice (focused) > Integration (complete)
- Right Tool: Use the narrowest slice that gives you confidence
- AssertJ Style: Fluent, readable assertions over verbose matchers
- Modern APIs: Prefer MockMvcTester and RestTestClient over legacy alternatives
Which Test Slice?
| Scenario | Annotation | Reference |
|---|---|---|
| Controller + HTTP semantics | @WebMvcTest | references/webmvctest.md |
| Repository + JPA queries | @DataJpaTest | references/datajpatest.md |
| REST client + external APIs | @RestClientTest | references/restclienttest.md |
| JSON (de)serialization | @JsonTest | See references/test-slices-overview.md |
| Full application | @SpringBootTest | See references/test-slices-overview.md |
Test Slices Reference
- references/test-slices-overview.md - Decision matrix and comparison
- references/webmvctest.md - Web layer with MockMvc
- references/datajpatest.md - Data layer with Testcontainers
- references/restclienttest.md - REST client testing
Testing Tools Reference
- references/mockmvc-tester.md - AssertJ-style MockMvc (3.2+)
- references/mockmvc-classic.md - Traditional MockMvc (pre-3.2)
- references/resttestclient.md - Spring Boot 4+ REST client
- references/mockitobean.md - Mocking dependencies
Assertion Libraries
- references/assertj-basics.md - Scalars, strings, booleans, dates
- references/assertj-collections.md - Lists, Sets, Maps, arrays
Testcontainers
- references/testcontainers-jdbc.md - PostgreSQL, MySQL, etc.
Test Data Generation
- references/instancio.md - Generate complex test objects (3+ properties)
Performance & Migration
- references/context-caching.md - Speed up test suites
- references/sb4-migration.md - Spring Boot 4.0 changes
Quick Decision Tree
Testing a controller endpoint?
Yes → @WebMvcTest with MockMvcTester
Testing repository queries?
Yes → @DataJpaTest with Testcontainers (real DB)
Testing business logic in service?
Yes → Plain JUnit + Mockito (no Spring context)
Testing external API client?
Yes → @RestClientTest with MockRestServiceServer
Testing JSON mapping?
Yes → @JsonTest
Need full integration test?
Yes → @SpringBootTest with minimal context config
Spring Boot 4 Highlights
- RestTestClient: Modern alternative to TestRestTemplate
- @MockitoBean: Replaces @MockBean (deprecated)
- MockMvcTester: AssertJ-style assertions for web tests
- Modular starters: Technology-specific test starters
- Context pausing: Automatic pausing of cached contexts (Spring Framework 7)
Testing Best Practices
Code Complexity Assessment
When a method or class is too complex to test effectively:
- Analyze complexity - If you need more than 5-7 test cases to cover a single method, it's likely too complex
- Recommend refactoring - Suggest breaking the code into smaller, focused functions
- User decision - If the user agrees to refactor, help identify extraction points
- Proceed if needed - If the user decides to continue with the complex code, implement tests despite the difficulty
Example of refactoring recommendation:
// Before: Complex method hard to test
public Order processOrder(OrderRequest request) {
// Validation, discount calculation, payment, inventory, notification...
// 50+ lines of mixed concerns
}
// After: Refactored into testable units
public Order processOrder(OrderRequest request) {
validateOrder(request);
var order = createOrder(request);
applyDiscount(order);
processPayment(order);
updateInventory(order);
sendNotification(order);
return order;
}
Avoid Code Redundancy
Create helper methods for commonly used objects and mock setup to enhance readability and maintainability.
Test Organization with @DisplayName
Use descriptive display names to clarify test intent:
@Test
@DisplayName("Should calculate discount for VIP customer")
void shouldCalculateDiscountForVip() { }
@Test
@DisplayName("Should reject order when customer has insufficient credit")
void shouldRejectOrderForInsufficientCredit() { }
Test Coverage Order
Always structure tests in this order:
- Main scenario - The happy path, most common use case
- Other paths - Alternative valid scenarios, edge cases
- Exceptions/Errors - Invalid inputs, error conditions, failure modes
Test Production Scenarios
Write tests with real production scenarios in mind. This makes tests more relatable and helps understand code behavior in actual production cases.
Test Coverage Goals
Aim for 80% code coverage as a practical balance between quality and effort. Higher coverage is beneficial but not the only goal.
Use Jacoco maven plugin for coverage reporting and tracking.
Coverage Rules:
- 80+% coverage minimum
- Focus on meaningful assertions, not just execution
What to Prioritize:
- Business-critical paths (payment processing, order validation)
- Complex algorithms (pricing, discount calculations)
- Error handling (exceptions, edge cases)
- Integration points (external APIs, databases)
Dependencies (Spring Boot 4)
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<!-- For WebMvc tests -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-webmvc-test</artifactId>
<scope>test</scope>
</dependency>
<!-- For Testcontainers -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-testcontainers</artifactId>
<scope>test</scope>
</dependency>
FAQ
What does the spring-boot-testing skill do?
Expert Spring Boot 4 testing specialist that selects the best Spring Boot testing techniques for your situation with Junit 6 and AssertJ.
How do I install spring-boot-testing?
Run npx skills add https://github.com/marcelorodrigo/agent-skills --skill spring-boot-testing in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/spring-boot-testing/ (personal) or .claude/skills/spring-boot-testing/ (project).
Which AI agents can use spring-boot-testing?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is spring-boot-testing safe to install?
No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.
Who maintains spring-boot-testing?
It is published by marcelorodrigo in marcelorodrigo/agent-skills. It has 215 recorded installs.
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