Agent skill

131 Java Testing Unit Testing

A skill your agent uses 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…

Apache-2.0Auto-check passedTesting & QA

Install 131 Java Testing Unit Testing

skills CLI

$ npx skills add jabrena/plinth --skill 131-java-testing-unit-testing -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI

$ gh skill install jabrena/plinth 131-java-testing-unit-testing --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy

$ git clone --depth 1 https://github.com/jabrena/plinth.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/131-java-testing-unit-testing .claude/skills/131-java-testing-unit-testing && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Paste into Claude Code

Install the "131-java-testing-unit-testing" agent skill from https://github.com/jabrena/plinth/tree/main/skills/131-java-testing-unit-testing into .claude/skills/131-java-testing-unit-testing/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "131-java-testing-unit-testing", then confirm the skill loads.

Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

$skill-installer

$skill-installer install https://github.com/jabrena/plinth/tree/main/skills/131-java-testing-unit-testing

Type this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.

skills CLI

$ npx skills add jabrena/plinth --skill 131-java-testing-unit-testing -a codex

Project install goes to .agents/skills/; add -g for ~/.codex/skills/.

GitHub CLI

$ gh skill install jabrena/plinth 131-java-testing-unit-testing --agent codex

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/jabrena/plinth.git skills-src && mkdir -p .agents/skills && cp -r skills-src/skills/131-java-testing-unit-testing .agents/skills/131-java-testing-unit-testing && rm -rf skills-src

Use ~/.agents/skills/ instead of .agents/skills for a personal install.

Codex skills documentation · loads skills from .agents/skills/

Paste into Codex

Install the "131-java-testing-unit-testing" agent skill from https://github.com/jabrena/plinth/tree/main/skills/131-java-testing-unit-testing into .agents/skills/131-java-testing-unit-testing/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "131-java-testing-unit-testing", then confirm the skill loads.

Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add jabrena/plinth --skill 131-java-testing-unit-testing -a cursor

Project install goes to .agents/skills/; add -g for ~/.cursor/skills/.

GitHub CLI

$ gh skill install jabrena/plinth 131-java-testing-unit-testing --agent cursor

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/jabrena/plinth.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/skills/131-java-testing-unit-testing .cursor/skills/131-java-testing-unit-testing && rm -rf skills-src

Use ~/.cursor/skills/ instead of .cursor/skills for a personal install.

Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/

Paste into Cursor

Install the "131-java-testing-unit-testing" agent skill from https://github.com/jabrena/plinth/tree/main/skills/131-java-testing-unit-testing into .cursor/skills/131-java-testing-unit-testing/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "131-java-testing-unit-testing", then confirm the skill loads.

Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

gemini skills install

$ gemini skills install https://github.com/jabrena/plinth.git --path skills/131-java-testing-unit-testing

--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.

skills CLI

$ npx skills add jabrena/plinth --skill 131-java-testing-unit-testing -a gemini-cli

Project install goes to .agents/skills/; add -g for ~/.gemini/skills/.

GitHub CLI

$ gh skill install jabrena/plinth 131-java-testing-unit-testing --agent gemini-cli

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/jabrena/plinth.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/skills/131-java-testing-unit-testing .gemini/skills/131-java-testing-unit-testing && rm -rf skills-src

Use ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.

Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/

Paste into Gemini CLI

Install the "131-java-testing-unit-testing" agent skill from https://github.com/jabrena/plinth/tree/main/skills/131-java-testing-unit-testing into .gemini/skills/131-java-testing-unit-testing/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "131-java-testing-unit-testing", then confirm the skill loads.

Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

GitHub CLI

$ gh skill install jabrena/plinth 131-java-testing-unit-testing

Installs for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).

skills CLI

$ npx skills add jabrena/plinth --skill 131-java-testing-unit-testing -a github-copilot

Project install goes to .agents/skills/; add -g for ~/.copilot/skills/.

Manual copy

$ git clone --depth 1 https://github.com/jabrena/plinth.git skills-src && mkdir -p .github/skills && cp -r skills-src/skills/131-java-testing-unit-testing .github/skills/131-java-testing-unit-testing && rm -rf skills-src

Use ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.

GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/

Paste into GitHub Copilot

Install the "131-java-testing-unit-testing" agent skill from https://github.com/jabrena/plinth/tree/main/skills/131-java-testing-unit-testing into .github/skills/131-java-testing-unit-testing/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "131-java-testing-unit-testing", then confirm the skill loads.

GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add jabrena/plinth --skill 131-java-testing-unit-testing -a opencode

OpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.

GitHub CLI

$ gh skill install jabrena/plinth 131-java-testing-unit-testing --agent opencode

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/jabrena/plinth.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/skills/131-java-testing-unit-testing .opencode/skills/131-java-testing-unit-testing && rm -rf skills-src

Use ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.

OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/

Paste into OpenCode

Install the "131-java-testing-unit-testing" agent skill from https://github.com/jabrena/plinth/tree/main/skills/131-java-testing-unit-testing into .opencode/skills/131-java-testing-unit-testing/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "131-java-testing-unit-testing", then confirm the skill loads.

OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

Facts

Skill name: 131-java-testing-unit-testing
GitHub stars: 446
Token cost: ~902 tokens
SKILL.md length: 315 words
Files: 2 (incl. references)
Skills in repo: 124
Repo updated: Oct 7, 2026
First seen: Oct 7, 2026
Licence: Apache-2.0

At a glance

A skill your agent uses 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…

You need to review
SKILL.md covers Constraints, When to use this skill, Workflow and Reference
Calls mvn
Write Java unit tests — including migrating from JUnit 4 to JUnit 5

What it does

131 Java Testing Unit Testing is an agent skill from jabrena/plinth. 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…

Its SKILL.md is about 900 tokens, which your agent loads only when the skill is triggered. The skill folder holds 2 other files, including reference files (for example `references/131-java-testing-unit-testing.md`).

It sits in Testing & QA, covering Unit testing. It works with Java, JUnit and Bicep. The repository describes itself as: Plinth is an AI-native engineering toolkit for modern Java enterprise SDLC, built around reusable Commands, Agents, Skills, and MCP Servers. The licence is Apache-2.0.

When your agent uses it

You need to review
Write Java unit tests — including migrating from JUnit 4 to JUnit 5
Adopting AssertJ for fluent assertions
Structuring tests with Given-When-Then

Example prompts

“/131-java-testing-unit-testing”

What it can do on your machine

Read from SKILL.md and the folder at commit dca88dc. It shows what the files ask for, not the result of running them.

Tool permissions
Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.
From allowed-tools in the SKILL.md frontmatter.
Runs code
Shell commands in SKILL.md call:
- mvn
From the folder's file list and the shell code blocks in SKILL.md.
Network
No URLs in SKILL.md.
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

131 Java Testing Unit Testing loads about 902 tokens when it runs, and up to ~8.8k if it reads all its reference files. Until then it costs about 197 tokens; SKILL.md has 315 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it: ~197
When it runs · the whole SKILL.md, loaded when a task matches: ~902
With references · SKILL.md plus every file in references/, read only if the agent opens them: ~8.8k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from jabrena/plinth at commit dca88dc, republished under its Apache-2.0 licence (© jabrena). 315 words, ~902 tokens.

Download SKILL.mdSave it as .claude/skills/131-java-testing-unit-testing/SKILL.md (or your agent's skills folder). This skill also uses 1 other file; get the full folder from GitHub.

name: 131-java-testing-unit-testing
description: 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
license: Apache-2.0
metadata.author: Juan Antonio Breña Moral
metadata.version: 0.19.0

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

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.

Files

SKILL.md and 1 other file (references) in skills/131-java-testing-unit-testing of jabrena/plinth.

SKILL.md
references/131-java-testing-unit-testing.md

Open the folder on GitHubat commit dca88dc

Compare with similar skills

131 Java Testing Unit Testing next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

131 Java Testing Unit Testing compared with similar skills
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131 Java Testing Unit Testing this skilljabrena/plinth	446	—	~902	Automated safety check: Pass	Apache-2.0	today
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Minecraft TestingJahrome907/minecraft-agent-skills	166	—	~3.8k	Automated safety check: Pass	MIT	25 days ago
Eclipse Testgradusnikov/eclipse-chatgpt-plugin	171	—	~1k	Automated safety check: Pass	MIT	10 days ago
Unit TestingLeavesfly/Jimi	237	—	~667	Automated safety check: Pass	None	1 mo ago
Migrate Junit Source To TabletestDataDog/dd-trace-java	736	—	~950	Automated safety check: Pass	Apache-2.0	today

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Works with

Questions about 131 Java Testing Unit Testing

What does 131 Java Testing Unit Testing do?

A skill your agent uses 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…. 131 Java Testing Unit Testing is an agent skill from jabrena/plinth. 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.

When should I use 131 Java Testing Unit Testing?

131 Java Testing Unit Testing fits situations like: you need to review; write Java unit tests — including migrating from JUnit 4 to JUnit 5; adopting AssertJ for fluent assertions; structuring tests with Given-When-Then.

How do I install 131 Java Testing Unit Testing in Claude Code?

Run `npx skills add jabrena/plinth --skill 131-java-testing-unit-testing -a claude-code`. Or copy the skill folder (skills/131-java-testing-unit-testing in jabrena/plinth) into .claude/skills/131-java-testing-unit-testing in your project. Claude Code loads it when a task matches its description.

How do I install 131 Java Testing Unit Testing in Codex?

Run `npx skills add jabrena/plinth --skill 131-java-testing-unit-testing -a codex`. Or copy the skill folder (skills/131-java-testing-unit-testing in jabrena/plinth) into .agents/skills/131-java-testing-unit-testing in your project. Codex loads it when a task matches its description.

Can I use 131 Java Testing Unit Testing in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add jabrena/plinth --skill 131-java-testing-unit-testing -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/131-java-testing-unit-testing, .gemini/skills/131-java-testing-unit-testing, .github/skills/131-java-testing-unit-testing and .opencode/skills/131-java-testing-unit-testing in your project.

What does 131 Java Testing Unit Testing need to run?

Going by SKILL.md and its folder, 131 Java Testing Unit Testing needs the command-line tools its instructions call (mvn).

Does 131 Java Testing Unit Testing access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is 131 Java Testing Unit Testing safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does 131 Java Testing Unit Testing use?

131 Java Testing Unit Testing is published under the Apache-2.0 licence (declared in SKILL.md). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does 131 Java Testing Unit Testing use?

About 902 tokens (SKILL.md is roughly 3.6k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 7.9k tokens, read only when the agent opens those files.

What are the alternatives to 131 Java Testing Unit Testing?

Skills that share tags, products or a category with 131 Java Testing Unit Testing: Debug Surefire (eclipse-rdf4j/rdf4j, 420 stars), Minecraft Testing (Jahrome907/minecraft-agent-skills, 166 stars), Eclipse Test (gradusnikov/eclipse-chatgpt-plugin, 171 stars) and Unit Testing (Leavesfly/Jimi, 237 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains 131 Java Testing Unit Testing?

jabrena (a GitHub user) maintains it in jabrena/plinth, which has 446 GitHub stars. The repository holds 124 skills in this directory. The repository was last updated on October 7, 2026.

Source: jabrena/plinth on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.

Install 131 Java Testing Unit Testing

Facts

At a glance

What it does

When your agent uses it

Example prompts

What it can do on your machine

Tool permissions

Runs code

Network

Credentials

Context cost

Safety

SKILL.md

Java Unit testing guidelines

Constraints

When to use this skill

Workflow

Reference

Files

Compare with similar skills

Similar skills

More from jabrena/plinth

Related

Questions about 131 Java Testing Unit Testing