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java-testing — Claude Code skill: what it does, how to install

Generates unit and integration tests for Java services. Helps configure JUnit 5, Mockito stubs, and Testcontainers environments.

Install into Claude Code · Skills CLI (Vercel) All methods and platforms ↓ 
npx skills add pluginagentmarketplace/custom-plugin-java --skill java-testing -a claude-code
Open on GitHub

What java-testing does

This skill instructs the agent to create test suites for Java codebases. JUnit 5 acts as the default runner, with TestNG available as an option. The assistant handles unit checks, contract validations, and end-to-end flows. It structures Mockito mocks, AssertJ assertions, and builder patterns.

Integration workflows rely on Spring Boot test slices and Testcontainers. The skill also covers JaCoCo configuration for tracking code coverage.

Uninitialized mocks break test runs immediately. If @ExtendWith(MockitoExtension.class) is missing, Mockito stubs will not work. The skill includes a troubleshooting checklist for shared state issues and missing @MockBean entries. The agent requires file access tools (Read, Write, Glob, Grep) and terminal execution through Bash.

What it helps with

  • generate unit tests with Mockito mocks and AssertJ assertions
  • set up database integration tests with Testcontainers in Spring Boot
  • write parameterized test cases using @ParameterizedTest
  • resolve test failures caused by uninitialized mocks or missing Spring beans

Example prompts for the agent

  • Write a unit test for UserService using Mockito and AssertJ
  • Create an integration test for OrderRepository using Testcontainers with PostgreSQL
  • Add parameterized test cases for email validation in JUnit 5

How to install java-testing

1Skills CLI (Vercel)

npx skills add pluginagentmarketplace/custom-plugin-java --skill java-testing -a claude-code

2Manually: put the files in place

~/.claude/skills/java-testing/SKILL.md

Copy the whole skill folder; for one project use .claude/skills/java-testing/

Step by step, with commands for each platform: How to install skills in Claude Code: five ways

Questions about java-testing

How do I install java-testing in Claude Code?

Run npx skills add pluginagentmarketplace/custom-plugin-java --skill java-testing -a claude-code. The file will be placed in ~/.claude/skills/java-testing/SKILL.md.

Which testing frameworks are supported?

JUnit 5 is configured by default, and TestNG is available via skill parameters. You can generate unit, integration, contract, or end-to-end tests.

Which agent tools does java-testing need?

The skill expects file operations (Read, Write), file discovery (Glob, Grep), and shell access through Bash.

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