131-java-testing-unit-testing
Use when you need to review, improve, or write Java unit tests — including migrating from JUnit 4 to JUnit 5, adopting AssertJ for fluent assertions, structuring tests with Given-When-Then, ensuring test independence, applying parameterized tests, mocking dependencies with Mockito, verifying boundary conditions (RIGHT-BICEP, CORRECT, A-TRIP), leveraging JSpecify null-safety annotations, or eliminating testing anti-patterns such as reflection-based tests or shared mutable state. This should trigger for requests such as Review Java code for unit tests; Apply best practices for unit tests in Java code; Write fast JUnit unit tests for Java code; Improve Mockito-based Java unit tests; Refactor Java tests to isolate collaborators. Part of Plinth Toolkit
How do I install this agent skill?
npx skills add https://github.com/jabrena/plinth --skill 131-java-testing-unit-testingIs this agent skill safe to install?
- Gen Agent Trust Hubpass
The skill provides comprehensive guidelines and examples for modern Java unit testing using JUnit 5, AssertJ, and Mockito. It includes mandatory safety checks using standard build tools like Maven to verify code integrity, and it carries a low risk of indirect prompt injection as it is designed to process and modify project code.
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- Snykpass
Risk: LOW · No issues
What does this agent skill do?
Java Unit testing guidelines
Review and improve Java unit tests using modern JUnit 5, AssertJ, and Mockito best practices.
What is covered in this Skill?
- JUnit 5 annotations:
@Test,@BeforeEach,@AfterEach,@DisplayName,@Nested,@ParameterizedTest - AssertJ fluent assertions:
assertThat,assertThatThrownBy - Given-When-Then test structure, descriptive test naming, single-responsibility tests
- Test independence and isolated state
- Parameterized tests:
@ValueSource/@CsvSource/@MethodSource - Mockito dependency mocking:
@Mock,@InjectMocks,MockitoExtension - Code coverage guidance (JaCoCo), package-private test visibility
- Testing anti-patterns: reflection, shared state, hard-coded values, testing implementation details
- Error handling:
assertThatThrownBy, exception messages - JSpecify null-safety:
@NullMarked,@Nullable - RIGHT-BICEP coverage principles, A-TRIP test quality, CORRECT boundary condition verification
Scope: The reference is organized by examples (good/bad code patterns) for each core area. Apply recommendations based on applicable examples.
Constraints
Before applying any unit test changes, ensure the project compiles. If compilation fails, stop immediately — do not proceed until resolved. After applying improvements, run full verification.
- MANDATORY: Run
./mvnw compileormvn compilebefore applying any change - SAFETY: If compilation fails, stop immediately and do not proceed — compilation failure is a blocking condition
- VERIFY: Run
./mvnw clean verifyormvn clean verifyafter applying improvements - BEFORE APPLYING: Read the reference for detailed examples, good/bad patterns, and constraints
When to use this skill
- Review Java code for unit tests
- Apply best practices for unit tests in Java code
- Write fast JUnit unit tests for Java code
- Improve Mockito-based Java unit tests
- Refactor Java tests to isolate collaborators
Workflow
- Compile project before unit-test changes
Run ./mvnw compile or mvn compile and stop immediately if compilation fails.
- Read unit-testing reference and evaluate coverage
Read references/131-java-testing-unit-testing.md and identify modernization and quality gaps in current tests.
- Apply unit-testing best practices
Implement or refactor tests using JUnit 5, AssertJ, Mockito, parameterization, and stronger boundary checks.
- Verify with full build
Run ./mvnw clean verify or mvn clean verify after applying improvements.
Reference
For detailed guidance, examples, and constraints, see references/131-java-testing-unit-testing.md.
How can the creator link this skill?
Add the canonical catalog link to the repository README so users can inspect current installs and available audits. The publishing guide covers the complete discovery path.
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