# Test Design Patterns

> Apply testing patterns like AAA (Arrange-Act-Assert), mocking, fixtures, and parameterization for maintainable test suites

- Skill: `majiayu000/test-design-patterns` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add majiayu000/test-design-patterns`
- Raw SKILL.md: https://api.skillmd.com/api/skills/majiayu000/test-design-patterns/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: majiayu000 (https://skillmd.com/u/majiayu000)
- Updated: 2026-09-09
- Page: https://skillmd.com/skills/majiayu000/test-design-patterns

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# Test Design Patterns

## Purpose
Apply proven testing patterns to create maintainable, reliable test suites that effectively validate functionality.

## When to Use
- Writing unit, integration, or system tests
- Organizing test code
- Creating test fixtures and data
- Designing test strategies

## Key Capabilities
1. **AAA Pattern** - Arrange-Act-Assert structure
2. **Test Fixtures** - Reusable test data and setup
3. **Mocking/Stubbing** - Isolate units under test

## Approach
1. **Arrange**: Set up test data and conditions
2. **Act**: Execute the code being tested
3. **Assert**: Verify expected outcomes
4. Use descriptive test names
5. Keep tests independent and isolated

## Example
**Context**: Testing a task creation function
````python
def test_add_task_with_valid_input_creates_task():
    # Arrange
    queue = TaskQueue()
    task_data = {"title": "Test", "agent": "tester"}
    
    # Act
    task_id = queue.add_task(task_data)
    
    # Assert
    assert task_id is not None
    assert queue.get_task(task_id).title == "Test"
````

## Best Practices
- ✅ One logical assertion per test
- ✅ Descriptive test names explaining scenario
- ✅ Independent tests (no shared state)
- ❌ Avoid: Testing multiple unrelated things together