Framework	Purpose
Vitest	Unit/Integration tests
Playwright	E2E tests
Testing Library	Component tests

Test Structure (AAA Pattern)

describe('functionName', () => {
  it('should [expected behavior] when [condition]', () => {
    // Arrange
    const input = createTestInput();

    // Act
    const result = functionName(input);

    // Assert
    expect(result).toBe(expectedValue);
  });
});

Test Categories

1. Happy Path

it('should return sum when given valid numbers', () => {
  expect(add(2, 3)).toBe(5);
});

2. Edge Cases

it('should handle empty array', () => {
  expect(sum([])).toBe(0);
});

it('should handle single element', () => {
  expect(sum([5])).toBe(5);
});

it('should handle negative numbers', () => {
  expect(sum([-1, 1])).toBe(0);
});

3. Error Cases

it('should throw on invalid input', () => {
  expect(() => divide(10, 0)).toThrow('Division by zero');
});

it('should throw on null input', () => {
  expect(() => process(null)).toThrow(TypeError);
});

4. Async Tests

it('should fetch user data', async () => {
  const user = await fetchUser(1);
  expect(user.name).toBe('John');
});

it('should handle API errors', async () => {
  await expect(fetchUser(-1)).rejects.toThrow('Not found');
});

Mocking

Mock Functions

import { vi } from 'vitest';

const mockFn = vi.fn();
mockFn.mockReturnValue(42);
mockFn.mockResolvedValue({ data: 'test' });

Mock Modules

vi.mock('./database', () => ({
  query: vi.fn().mockResolvedValue([{ id: 1 }]),
}));

Spies

const spy = vi.spyOn(console, 'log');
doSomething();
expect(spy).toHaveBeenCalledWith('expected message');

Coverage Requirements

Metric	Target
Statements	80%
Branches	80%
Functions	80%
Lines	80%

# Run with coverage
npm test -- --coverage

Test File Naming

src/
├── utils/
│   ├── helper.ts
│   └── helper.test.ts      # Co-located
└── __tests__/
    └── integration.test.ts  # Integration tests

Template

import { describe, it, expect, beforeEach, vi } from 'vitest';
import { functionName } from './module';

describe('functionName', () => {
  beforeEach(() => {
    vi.clearAllMocks();
  });

  describe('when input is valid', () => {
    it('should return expected result', () => {
      // Arrange
      const input = { /* ... */ };

      // Act
      const result = functionName(input);

      // Assert
      expect(result).toEqual(expected);
    });
  });

  describe('when input is invalid', () => {
    it('should throw error', () => {
      expect(() => functionName(null)).toThrow();
    });
  });

  describe('edge cases', () => {
    it.each([
      [[], 0],
      [[1], 1],
      [[1, 2], 3],
    ])('sum(%j) = %i', (input, expected) => {
      expect(sum(input)).toBe(expected);
    });
  });
});

Test Structure (AAA Pattern)

Test Categories

1. Happy Path

2. Edge Cases

3. Error Cases

4. Async Tests

Mocking

Mock Functions

Mock Modules

Spies

Coverage Requirements

Test File Naming

Template

Checklist

Trigger	Examples
Test creation	"write tests", "テスト作成", "add unit tests"
Coverage	"improve coverage", "カバレッジ向上"
TDD	"test first", "TDDで"

test-generator

Test Generator

Triggers

Testing Stack

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