java-testing-advanced — Claude Code skill: Testcontainers, Pact, PIT
A Java testing skill that spins up real databases and Kafka in containers, checks API contracts, and hunts coverage gaps with mutation testing.
npx skills add pluginagentmarketplace/custom-plugin-java --skill java-testing-advanced -a claude-codeWhat java-testing-advanced does
The skill hands your agent four advanced Java testing techniques. Testcontainers starts PostgreSQL and Kafka inside the test, and @DynamicPropertySource wires their addresses into the Spring config. Pact contract tests describe what the consumer expects and run it against a mock server. Mutation testing is configured through the pitest-maven plugin with a mutation threshold. Property-based tests check invariants against generated data.
Inside are ready code samples for each technique plus a troubleshooting table: slow containers, port conflicts, flaky tests. A technique parameter takes testcontainers, contract, mutation or property_based, so the agent picks the right branch from your prompt.
Testcontainers needs Docker running on the machine — without it the integration tests never start. The sample sets the mutation threshold to 80, which is worth checking against your project before you wire it into the build.
What it helps with
- run integration tests against a real PostgreSQL and Kafka
- verify the contract between a consumer service and its provider
- find untested branches with mutation testing
- generate test cases from random data instead of hand-written examples
- deal with slow containers and port conflicts
Example prompts for the agent
- Set up Testcontainers for the order repository test with PostgreSQL and Kafka
- Add a Pact contract test between order-service and user-service
- Configure pitest-maven with a mutation threshold of 80 for com.example.service
How to install java-testing-advanced
1Skills CLI (Vercel)
npx skills add pluginagentmarketplace/custom-plugin-java --skill java-testing-advanced -a claude-code2Manually: put the files in place
~/.claude/skills/java-testing-advanced/SKILL.mdCopy the whole skill folder; for one project use .claude/skills/java-testing-advanced/
1Skills CLI (Vercel)
npx skills add pluginagentmarketplace/custom-plugin-java --skill java-testing-advanced -a codex2Manually: put the files in place
.agents/skills/java-testing-advanced/SKILL.mdFor all projects use ~/.agents/skills/
1Skills CLI (Vercel)
npx skills add pluginagentmarketplace/custom-plugin-java --skill java-testing-advanced -a cursor2Manually: put the files in place
.cursor/skills/java-testing-advanced/SKILL.mdCursor also reads .agents/skills/ and .claude/skills/
1GitHub CLI
gh skill install pluginagentmarketplace/custom-plugin-java java-testing-advanced2Manually: put the files in place
.github/skills/java-testing-advanced/SKILL.md1Skills CLI (Vercel)
npx skills add pluginagentmarketplace/custom-plugin-java --skill java-testing-advanced -a gemini-cli2Platform CLI
gemini skills install https://github.com/pluginagentmarketplace/custom-plugin-java --path skills/java-testing-advancedManually: put the files in place
.devin/skills/java-testing-advanced/SKILL.mdThe legacy .windsurf/skills/ path still works
Skills CLI (Vercel)
npx skills add pluginagentmarketplace/custom-plugin-java --skill java-testing-advanced -a opencodeClaude.ai
Zip the folder and upload it in Settings → Capabilities → Skills
Step by step, with commands for each platform: How to install skills in Claude Code: five ways
Questions about java-testing-advanced
How do I install java-testing-advanced in Claude?
Run npx skills add pluginagentmarketplace/custom-plugin-java --skill java-testing-advanced -a claude-code. The skill file then lands at ~/.claude/skills/java-testing-advanced/SKILL.md.
What does java-testing-advanced do?
It gives the agent templates and configuration for Testcontainers, Pact contract testing, PIT mutation testing and property-based tests.
What does Testcontainers need in this skill?
The examples start PostgreSQL and Kafka in containers, so Docker has to be available on the machine. Without it the integration tests will not run.
