tests/
├── unit/                     # Unit tests (Vitest)
│   └── *.test.ts
└── e2e/                      # E2E tests (Playwright)
    ├── fixtures/
    │   ├── index.ts          # Custom fixtures (auth, db, cleanup)
    │   ├── auth.fixture.ts   # Authentication helpers
    │   └── db.fixture.ts     # Database connection & cleanup
    ├── pages/                # Page Object Model
    │   ├── base.page.ts      # Base page with common methods
    │   ├── login.page.ts
    │   └── register.page.ts
    ├── flows/                # User flow tests
    │   ├── auth.spec.ts      # Login, register, logout
    │   ├── crud.spec.ts      # Create, read, update, delete
    │   └── permissions.spec.ts
    ├── api/                  # API-only tests (no UI)
    │   ├── rest.spec.ts      # REST API tests
    │   └── trpc.spec.ts      # tRPC API tests
    └── playwright.config.ts

// tests/e2e/fixtures/index.ts
import { test as base, expect } from '@playwright/test';
import { MongoClient, Db, ObjectId } from 'mongodb';

type TestFixtures = {
	db: Db;
	createdIds: Map<string, ObjectId[]>;
	trackCreated: (collection: string, id: ObjectId) => void;
};

export const test = base.extend<TestFixtures>(
	{
		db: async ({}, use) => {
			const client = await MongoClient.connect(process.env.MONGODB_URI!);
			const db = client.db();
			await use(db);
			await client.close();
		},

		createdIds: async ({}, use) => {
			const ids = new Map<string, ObjectId[]>();
			await use(ids);
		},

		trackCreated: async ({ createdIds }, use) => {
			const track = (collection: string, id: ObjectId) => {
				const existing = createdIds.get(collection) || [];
				existing.push(id);
				createdIds.set(collection, existing);
			};
			await use(track);
		},

		// AUTO-CLEANUP runs EVEN IF test fails
	},
	async ({ db, createdIds }, use) => {
		await use();

		for (const [collection, ids] of createdIds.entries()) {
			if (ids.length > 0) {
				await db.collection(collection).deleteMany({
					_id: { $in: ids },
				});
			}
		}
	}
);

export { expect };

// tests/e2e/fixtures/auth.fixture.ts
import { Page } from '@playwright/test';

export interface TestUser {
	name: string;
	email: string;
	password: string;
}

export function generateTestUser(): TestUser {
	const timestamp = Date.now();
	const random = Math.random().toString(36).substring(7);
	return {
		name: `Test User ${timestamp}`,
		email: `testuser_${timestamp}_${random}@test.com`,
		password: 'TestPassword123!',
	};
}

export async function registerUser(page: Page, user: TestUser): Promise<void> {
	await page.goto('/auth/register');
	await page.getByTestId('name-input').fill(user.name);
	await page.getByTestId('email-input').fill(user.email);
	await page.getByTestId('password-input').fill(user.password);
	await page.getByTestId('confirm-password-input').fill(user.password);
	await page.getByTestId('submit-button').click();
	await page.waitForURL(/\/app/, { timeout: 10000 });
}

export async function loginUser(page: Page, user: TestUser): Promise<void> {
	await page.goto('/auth/login');
	await page.getByTestId('email-input').fill(user.email);
	await page.getByTestId('password-input').fill(user.password);
	await page.getByTestId('submit-button').click();
	await page.waitForURL(/\/app/, { timeout: 10000 });
}

import { test, expect } from '../fixtures';
import { generateTestUser, registerUser } from '../fixtures/auth.fixture';

test.describe('[Feature] Flow', () => {
	test('complete user journey', async ({ page, db, trackCreated }) => {
		const user = generateTestUser();

		// 1. Register
		await registerUser(page, user);

		// 2. Verify in database
		const dbUser = await db.collection('users').findOne({
			email: user.email,
		});
		expect(dbUser).toBeTruthy();
		trackCreated('users', dbUser!._id); // TRACK FOR CLEANUP

		// 3. Create item
		await page.goto('/items/new');
		await page.getByTestId('title-input').fill('Test Item');
		await page.getByTestId('submit-button').click();

		// 4. Verify item in DB
		const item = await db.collection('items').findOne({
			userId: dbUser!._id,
		});
		expect(item).toBeTruthy();
		trackCreated('items', item!._id); // TRACK FOR CLEANUP

		// Test continues... cleanup is automatic
	});
});

import { test, expect } from '../fixtures';

test.describe('Responsive Design', () => {
	const viewports = [
		{ name: 'mobile', width: 375, height: 667 },
		{ name: 'tablet', width: 768, height: 1024 },
		{ name: 'desktop', width: 1280, height: 800 },
	];

	for (const viewport of viewports) {
		test(`layout works on ${viewport.name}`, async ({ page }) => {
			await page.setViewportSize(viewport);
			await page.goto('/');

			if (viewport.width < 768) {
				// Mobile: hamburger menu
				await expect(page.getByTestId('hamburger-menu')).toBeVisible();
				await expect(page.getByTestId('sidebar')).toBeHidden();
			} else {
				// Desktop: sidebar visible
				await expect(page.getByTestId('sidebar')).toBeVisible();
			}
		});
	}
});

import { test, expect } from '@playwright/test';

test.describe('REST API', () => {
	test('requires authentication', async ({ request }) => {
		const response = await request.get('/api/users');
		expect(response.status()).toBe(401);
	});

	test('validates input', async ({ request }) => {
		const response = await request.post('/api/users', {
			data: { email: 'invalid' },
		});
		expect(response.status()).toBe(400);
	});
});

import { test, expect } from '@playwright/test';

test.describe('tRPC API', () => {
	test('query without auth fails', async ({ request }) => {
		const response = await request.get('/api/trpc/user.me');
		expect(response.status()).toBe(401);
	});

	test('mutation validates input', async ({ request }) => {
		const response = await request.post('/api/trpc/user.create', {
			data: { json: { name: '' } },
		});
		const body = await response.json();
		expect(body.error).toBeDefined();
	});
});

import { test, expect } from '../fixtures';

test.describe('Security - Forbidden Requests', () => {
	test('cannot access other users data', async ({ page, db }) => {
		const userA = await createTestUser(db);
		const userB = await createTestUser(db);

		await loginAs(page, userA);

		// Try to access user B's data
		const response = await page.request.get(`/api/users/${userB._id}`);
		expect(response.status()).toBe(403);

		// Verify nothing changed in DB
		const unchanged = await db.collection('users').findOne({
			_id: userB._id,
		});
		expect(unchanged).toEqual(userB);
	});
});

import { describe, it, expect } from 'vitest';

describe('[Feature]', () => {
	describe('success cases', () => {
		it('should [expected behavior] when [condition]', () => {
			// Arrange
			// Act
			// Assert
		});
	});

	describe('error cases', () => {
		it('should throw when [invalid condition]', () => {
			expect(() => fn(invalid)).toThrow();
		});
	});
});

<!-- Forms -->
<input data-testid="name-input" />
<input data-testid="email-input" />
<input data-testid="password-input" />
<input data-testid="confirm-password-input" />
<button data-testid="submit-button" />

<!-- Feedback -->
<div data-testid="error-message" />
<div data-testid="success-message" />
<div data-testid="loading-spinner" />

<!-- Navigation -->
<nav data-testid="sidebar" />
<button data-testid="hamburger-menu" />
<nav data-testid="mobile-nav" />
<button data-testid="logout-button" />

<!-- Actions -->
<button data-testid="delete-button" />
<button data-testid="edit-button" />
<button data-testid="confirm-delete" />

# Install
bun add -D @playwright/test
bunx playwright install

# Run
bunx playwright test              # All tests
bunx playwright test --ui         # UI mode (recommended)
bunx playwright test --headed     # See browser
bunx playwright test --debug      # Debug mode

# Specific
bunx playwright test flows/auth   # Specific folder
bunx playwright test --project="iPhone SE"  # Specific viewport

# Reports
bunx playwright show-report

// WRONG - Skipping tests
test.skip("should work when authenticated", ...);

// WRONG - Mocking auth
const mockAuth = () => { /* fake */ };

// WRONG - Fixed test user
const testUser = { email: "test@test.com" };

// WRONG - No cleanup
const user = await db.create({ ... });  // Orphaned!

// WRONG - No DB validation
await page.click('submit');
// Just trust the UI? NO!

# Check coverage meets threshold
bash .claude/skills/test-coverage/scripts/coverage-check.sh 80

# Run E2E tests
bunx playwright test

# Run with UI
bunx playwright test --ui