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131-java-testing-unit-testing

131-java-testing-unit-testing

github.com/jabrenaTesting & quality456454 installsUpdated 1d ago
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About 131-java-testing-unit-testing

A skill for reviewing and improving Java unit tests with JUnit 5, AssertJ, and Mockito. It combines test-quality guidance and examples with compile-before-change and full-verification requirements.

Key features

  1. 01JUnit 5 structure and parameterized tests
  2. 02AssertJ fluent assertions
  3. 03Mockito dependency mocking
  4. 04Coverage and boundary-testing guidance
  5. 05Compile first, then verify changes

Use cases

  1. 01Review and modernize Java unit tests
  2. 02Write fast JUnit unit tests
  3. 03Isolate collaborators in Mockito tests

Install

Copy the command and run it in a terminal.

$npx skills add https://github.com/jabrena/plinth --skill 131-java-testing-unit-testing

After installing, type/131-java-testing-unit-testingin Claude Code to confirm it loaded.

Bundled filesreferences/131-java-testing-unit-testing.md

Details

From the project README

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 compile or mvn compile before applying any change
  • SAFETY: If compilation fails, stop immediately and do not proceed — compilation failure is a blocking condition
  • VERIFY: Run ./mvnw clean verify or mvn clean verify after 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

  1. Compile project before unit-test changes

Run ./mvnw compile or mvn compile and stop immediately if compilation fails.

  1. Read unit-testing reference and evaluate coverage

Read references/131-java-testing-unit-testing.md and identify modernization and quality gaps in current tests.

  1. Apply unit-testing best practices

Implement or refactor tests using JUnit 5, AssertJ, Mockito, parameterization, and stronger boundary checks.

  1. 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.

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