Java Testing

pluginagentmarketplace/custom-plugin-java

Handles the full spectrum of Java testing from JUnit 5 unit tests to Testcontainers integration tests. You get Mockito mocking patterns, AssertJ assertions, Spring Boot test slices, and MockMvc for API testing. The examples are solid and cover the BDD style (given/when/then) which keeps tests readable. Includes parameterized tests, test builders for cleaner setup, and JaCoCo coverage configs targeting 80%. The troubleshooting guide actually addresses real problems like flaky tests from shared state and mock initialization failures. Works with both JUnit 5 and TestNG, though the examples lean heavily on JUnit. Good for greenfield test suites or modernizing older JUnit 4 codebases.

skills.sh installs: 909
GitHub stars: 42
last updated: Aug 21, 2026

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Install

$ npx -y skills add pluginagentmarketplace/custom-plugin-java --skill java-testing --agent claude-code

Installs into .claude/skills of the current project.

Files

Java Testing Skill

Write comprehensive tests for Java applications with modern testing practices.

Overview

This skill covers Java testing with JUnit 5, Mockito, AssertJ, and integration testing with Spring Boot Test and Testcontainers. Includes TDD patterns and test coverage strategies.

When to Use This Skill

Use when you need to:

Write unit tests with JUnit 5
Create mocks with Mockito
Build integration tests with Testcontainers
Implement TDD/BDD practices
Improve test coverage

Topics Covered

JUnit 5

@Test, @Nested, @DisplayName
@ParameterizedTest with sources
Lifecycle annotations
Extensions and custom annotations

Mockito

@Mock, @InjectMocks, @Spy
Stubbing (when/thenReturn)
Verification (verify, times)
BDD style (given/willReturn)

AssertJ

Fluent assertions
Collection assertions
Exception assertions
Custom assertions

Integration Testing

@SpringBootTest slices
Testcontainers setup
MockMvc for APIs
Database testing

Quick Reference

// Unit Test with Mockito
@ExtendWith(MockitoExtension.class)
class UserServiceTest {

    @Mock
    private UserRepository userRepository;

SKILL.md on GitHub

Details

Repository: github.com/pluginagentmarketplace/custom-plugin-java
Categories: Testing & QA, Java & JVM
First seen: Apr 16, 2026

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