| name | test-generator |
| description | Automatically suggest tests for new functions and components. Use when new code is written, functions added, or user mentions testing. Creates test scaffolding with Jest, Vitest, Pytest patterns. Triggers on new functions, components, test requests, testing mentions. |
| allowed-tools | Read, Write, Edit |
Test Generator Skill
Auto-suggest tests when you write new code.
When I Activate
- ✅ New function created
- ✅ New component added
- ✅ User mentions testing or tests
- ✅ Test file missing for implementation
- ✅ User asks "can you test this?"
What I Generate
Quick Test Scaffolding
- Basic happy path tests
- Null/undefined edge cases
- Simple error scenarios
- Framework-appropriate syntax (Jest/Vitest/Pytest)
What I Don't Do
- Comprehensive test suites → Use @test-engineer sub-agent
- Integration tests → Use @test-engineer sub-agent
- E2E test design → Use @test-engineer sub-agent
- Test strategy planning → Use @test-engineer sub-agent
Relationship with @test-engineer Sub-Agent
Me (Skill): Quick test scaffolding
@test-engineer (Sub-Agent): Comprehensive testing strategy
Workflow
- You write a function
- I auto-generate basic test structure
- You want full suite → Invoke @test-engineer sub-agent
- Sub-agent creates comprehensive tests
Examples
JavaScript Function
function calculateDiscount(price, percentage) {
if (price <= 0) throw new Error('Invalid price');
return price * (percentage / 100);
}
describe('calculateDiscount', () => {
it('calculates discount correctly', () => {
expect(calculateDiscount(100, 10)).toBe(10);
});
it('throws error for invalid price', () => {
expect(() => calculateDiscount(0, 10)).toThrow('Invalid price');
});
it('handles zero percentage', () => {
expect(calculateDiscount(100, 0)).toBe(0);
});
});
React Component
function UserCard({ user, onEdit }) {
return (
<div className="user-card">
<h2>{user.name}</h2>
<button onClick={() => onEdit(user.id)}>Edit</button>
</div>
);
}
import { render, screen, fireEvent } from '@testing-library/react';
describe('UserCard', () => {
const mockUser = { id: 1, name: 'John Doe' };
const mockOnEdit = jest.fn();
it('renders user name', () => {
render(<UserCard user={mockUser} onEdit={mockOnEdit} />);
expect(screen.getByText('John Doe')).toBeInTheDocument();
});
it('calls onEdit with user id when button clicked', () => {
render(<UserCard user={mockUser} onEdit={mockOnEdit} />);
fireEvent.click(screen.getByText('Edit'));
expect(mockOnEdit).toHaveBeenCalledWith(1);
});
});
Python Function
def fetch_user_data(user_id: int) -> dict:
if user_id <= 0:
raise ValueError("Invalid user ID")
return db.query("SELECT * FROM users WHERE id = ?", [user_id])
import pytest
def test_fetch_user_data_success():
"""Test successful user data retrieval"""
result = fetch_user_data(1)
assert isinstance(result, dict)
assert 'id' in result
def test_fetch_user_data_invalid_id():
"""Test with invalid user ID"""
with pytest.raises(ValueError, match="Invalid user ID"):
fetch_user_data(0)
def test_fetch_user_data_negative_id():
"""Test with negative ID"""
with pytest.raises(ValueError):
fetch_user_data(-1)
Framework Detection
I automatically detect your testing framework:
- JavaScript/TypeScript: Jest, Vitest, Mocha
- Python: pytest, unittest
- Java: JUnit
- Go: testing package
Detection based on:
- package.json dependencies
- requirements.txt
- Existing test files
- Import statements
Test Patterns
Unit Tests
test('adds numbers correctly', () => {
expect(add(2, 3)).toBe(5);
});
Component Tests
test('button click triggers callback', () => {
const onClick = jest.fn();
render(<Button onClick={onClick} />);
fireEvent.click(screen.getByRole('button'));
expect(onClick).toHaveBeenCalled();
});
Edge Cases
test('handles empty input', () => {
expect(processData([])).toEqual([]);
});
test('handles null input', () => {
expect(processData(null)).toBeNull();
});
When to Use Sub-Agent
Invoke @test-engineer for:
- Complete test suites (20+ tests)
- Integration test strategy
- E2E test planning
- Test coverage goals
- Complex mocking scenarios
Example:
Me: "Generated 3 basic tests for calculateDiscount()"
You: "@test-engineer create comprehensive test suite with all edge cases"
Sub-agent: [Creates 25+ tests covering all scenarios]
Sandboxing Compatibility
Works without sandboxing: ✅ Yes
Works with sandboxing: ✅ Yes
- Filesystem: Writes test files to project
- Network: None required
- Configuration: None required
Customization
Edit test templates:
cp -r ~/.claude/skills/development/test-generator \
~/.claude/skills/development/my-test-generator
Integration with Commands
/test-gen Command
/test-gen --file utils.js --framework jest --coverage 90
Tips
- Let me scaffold first - Review before invoking sub-agent
- Add TODOs - I include TODO comments for complex cases
- Framework consistency - I match your project's testing style
- Quick iteration - Regenerate if not satisfied
Related Tools
- @test-engineer: Comprehensive test suite creation
- code-reviewer skill: Flags code that needs testing
- /test-gen command: Full test generation workflow