# unit-test-bean-validation

Provides patterns for testing Jakarta Bean Validation constraints and custom validators in JUnit 5. Helps verify DTO logic without loading Spring context.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 4900 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-bean-validation/SKILL.md
- Updated: 2026-09-10
- HTML: https://affpapa.org/en/nevibecode/skills/unit-test-bean-validation

## What it does

This skill provides test patterns for JSR-380 constraints like `@NotNull`, `@Size`, `@Email`, `@Min`, and `@Max`. It also covers custom `@Constraint` implementations and cross-field validation rules. Spring Boot is not required.

Setup relies on `Validation.buildDefaultValidatorFactory()` inside `@BeforeEach`. Patterns cover violation assertions using `getPropertyPath()`, `getMessage()`, and `getInvalidValue()`. The skill also provides guidance on conditional rules via validation groups and parameterized checks with `@ParameterizedTest`.

Your project needs `jakarta.validation-api` and `hibernate-validator` in the test scope. Remember that constraints ignore null values by default. Omitting `@NotNull` next to `@Email` or `@Size` will allow nulls to pass validation, creating subtle test failures when verifying field constraints.

## Install

### Claude Code (native platform)

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

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

### Codex

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

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

### Cursor

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

2. **Manually: put the files in place**
- File: `.cursor/skills/unit-test-bean-validation/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-bean-validation
```

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

### Gemini CLI

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

### Windsurf (Devin Desktop)

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

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add giuseppe-trisciuoglio/developer-kit --skill unit-test-bean-validation -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-bean-validation/SKILL.md

## When to use it
- Test bean validation rules without the overhead of Spring Boot
- Write unit tests for custom `@Constraint` annotations and multi-field logic
- Verify conditional rules using validation groups and `@ParameterizedTest`
- Assert violation details such as property paths and error messages

## Example prompts
- Write a JUnit 5 unit test for @NotNull and @Email constraints in UserDto
- Generate tests for a custom cross-field password validator using AssertJ

## 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: d53bb130d6057a4f.

BEGIN THIRD-PARTY FILE d53bb130d6057a4f
````text
---
name: unit-test-bean-validation
description: Provides patterns for unit testing Jakarta Bean Validation (JSR-380), including @Valid, @NotNull, @Min, @Max, @Email constraints with Hibernate Validator. Generates custom validator tests, constraint violation assertions, validation groups, and parameterized validation tests. Validates data integrity logic without Spring context. Use when writing validation tests, bean validation tests, or testing custom constraint validators.
allowed-tools: Read, Write, Bash, Glob, Grep
---

# Unit Testing Jakarta Bean Validation

## Overview

This skill provides executable patterns for unit testing Jakarta Bean Validation annotations and custom validators using JUnit 5. Covers built-in constraints (`@NotNull`, `@Email`, `@Min`, `@Max`, `@Size`), custom `@Constraint` implementations, cross-field validation, and validation groups. Tests run in isolation without Spring context.

## When to Use

- Writing unit tests for Jakarta Bean Validation or JSR-380 constraints
- Testing custom `@Constraint` validators and constraint violation messages
- Testing bean validation logic in DTOs and request objects
- Verifying cross-field validation (e.g., password matching)
- Testing conditional validation with validation groups
- Fast validation tests without Spring Boot context

## Instructions

1. **Add dependencies**: Include `jakarta.validation-api` and `hibernate-validator` in test scope
2. **Create base test class**: Build `Validator` once in `@BeforeEach` using `Validation.buildDefaultValidatorFactory()`
3. **Test valid cases first**: Verify objects pass without violations
4. **Test invalid cases**: Assert constraint violations include correct property path and message
5. **Extract violation details**: Use `getPropertyPath()`, `getMessage()`, `getInvalidValue()`
6. **Test custom validators**: See `references/custom-validators.md` for patterns
7. **Use parameterized tests**: Test multiple inputs efficiently with `@ParameterizedTest`
8. **Group validation tests**: Use validation groups for conditional rules (see `references/advanced-patterns.md`)

## Examples

### Maven Setup

```xml
<dependency>
  <groupId>jakarta.validation</groupId>
  <artifactId>jakarta.validation-api</artifactId>
</dependency>
<dependency>
  <groupId>org.hibernate.validator</groupId>
  <artifactId>hibernate-validator</artifactId>
  <scope>test</scope>
</dependency>
<dependency>
  <groupId>org.assertj</groupId>
  <artifactId>assertj-core</artifactId>
  <scope>test</scope>
</dependency>
```
````
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