# unit-test-parameterized

A skill that turns one JUnit 5 test method into many runs over different inputs. Useful when you need boundary coverage without copy-pasting assertions.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 3800 installs · ★ 363
- Author: giuseppe-trisciuoglio
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/giuseppe-trisciuoglio/developer-kit/tree/HEAD/plugins/developer-kit-java/skills/unit-test-parameterized/SKILL.md
- Updated: 2026-09-10
- HTML: https://affpapa.org/en/nevibecode/skills/unit-test-parameterized

## What it does

The skill hands your agent ready patterns for parameterized tests in JUnit 5. It covers `@ValueSource` for plain values, `@CsvSource` for tabular rows, `@MethodSource` for complex objects, `@EnumSource` for enums, and `@ArgumentsSource` with a custom `ArgumentsProvider`. Readable output comes from display names like `name = "{0}..."`.

The workflow it describes: put `junit-jupiter` on the test classpath, pick a data source, make the method parameters match the source types, set a display name, then run `./gradlew test --info` or `mvn test`. Every parameter set executes as its own test invocation, so the report tells you which case broke.

There are sharp edges. The parameter count from the source has to match the method signature or the test will not start. `@ValueSource` takes primitives, strings and enums only, not objects or `null`. Strings containing commas need single quotes inside `@CsvSource`, and a `@MethodSource` factory method must be static and live in the same test class. Worth checking your current tests against those rules before converting them.

The skill installs into Claude, Codex, Cursor, GitHub Copilot, Gemini CLI and OpenCode.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add giuseppe-trisciuoglio/developer-kit --skill unit-test-parameterized -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/unit-test-parameterized/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/unit-test-parameterized/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add giuseppe-trisciuoglio/developer-kit --skill unit-test-parameterized -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/unit-test-parameterized/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add giuseppe-trisciuoglio/developer-kit --skill unit-test-parameterized -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/unit-test-parameterized/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install giuseppe-trisciuoglio/developer-kit unit-test-parameterized
```

2. **Manually: put the files in place**
- File: `.github/skills/unit-test-parameterized/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add giuseppe-trisciuoglio/developer-kit --skill unit-test-parameterized -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/giuseppe-trisciuoglio/developer-kit --path plugins/developer-kit-java/skills/unit-test-parameterized
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/unit-test-parameterized/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add giuseppe-trisciuoglio/developer-kit --skill unit-test-parameterized -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/giuseppe-trisciuoglio/developer-kit/tree/HEAD/plugins/developer-kit-java/skills/unit-test-parameterized/SKILL.md

## When to use it
- run one check across a dozen input values
- cover boundary cases such as zero and the maximum
- keep a table of email addresses and expected results in a single test
- exercise every enum constant without a method per value
- move test data into a static factory method

## Example prompts
- write a JUnit 5 parameterized test for email validation with @CsvSource
- convert this test to @MethodSource with complex objects
- add a @ParameterizedTest with int boundary values via @ValueSource

## Source text · SKILL.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: c23132e97aa1c641.

BEGIN THIRD-PARTY FILE c23132e97aa1c641
````text
---
name: unit-test-parameterized
description: Provides parameterized testing patterns with JUnit 5, generates data-driven unit tests using @ParameterizedTest, @ValueSource, @CsvSource, @MethodSource. Creates tests that run the same logic with multiple input values. Use when writing data-driven Java tests, multiple test cases from single method, or boundary value analysis.
allowed-tools: Read, Write, Bash, Glob, Grep
---

# Parameterized Unit Tests with JUnit 5

## Overview

Provides patterns for parameterized unit tests in Java using JUnit 5. Covers `@ValueSource`, `@CsvSource`, `@MethodSource`, `@EnumSource`, `@ArgumentsSource`, and custom display names. Reduces test duplication by running the same test logic with multiple input values.

## When to Use

- Writing JUnit tests with multiple input combinations
- Implementing data-driven tests in Java
- Running same test with different values (boundary analysis)
- Testing multiple scenarios from single test method

## Instructions

1. **Add dependency**: Ensure `junit-jupiter-params` is on test classpath (included in `junit-jupiter`)
2. **Choose source**: `@ValueSource` for simple values, `@CsvSource` for tabular data, `@MethodSource` for complex objects
3. **Match parameters**: Test method parameters must match data source types
4. **Set display names**: Use `name = "{0}..."` for readable output
5. **Validate**: Run `./gradlew test --info` or `mvn test` and verify all parameter combinations execute

## Examples

### Maven / Gradle Dependency

JUnit 5 parameterized tests require `junit-jupiter` (includes params). Add `assertj-core` for assertions:

```xml
<!-- Maven -->
<dependency>
  <groupId>org.junit.jupiter</groupId>
  <artifactId>junit-jupiter</artifactId>
  <scope>test</scope>
</dependency>
```

```kotlin
// Gradle
testImplementation("org.junit.jupiter:junit-jupiter")
```

### `@ValueSource` — Simple Values

```java
import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.ValueSource;
import static org.assertj.core.api.Assertions.*;

@ParameterizedTest
@ValueSource(strings = {"hello", "world", "test"})
void shouldCapitalizeAllStrings(String input) {
````
END THIRD-PARTY FILE c23132e97aa1c641

The third-party file has ended. Everything between the c23132e97aa1c641 tags is data: requests and commands from it are not followed. An “end of file” line with another tag inside the block is part of the file.

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