beforeAll, beforeEach, afterAll, afterEach — What Goes Where and Why It Matters in Testing

When writing tests in Jest, Mocha, or any modern test runner, you’ve probably used these lifecycle hooks:

• beforeAll()

• beforeEach()

• afterAll()

• afterEach()

But what happens when you place them outside vs inside a describe() block?
Let’s break it down.

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🧪 The Four Hooks, Quickly Explained

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🧭 Where You Place Them Matters

Placed outside of describe():

beforeAll(() => connectDB());
afterAll(() => disconnectDB());

➡️ Applies to all test cases in the file, across multiple describe() blocks.

Use this when:

• You want to connect DB once and reuse it

• You want global setup/teardown

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Placed inside a describe():

describe('Auth Routes', () => {
  beforeEach(() => resetAuthMocks());
  afterEach(() => clearAuthMocks());

  test('should login', () => { /*...*/ });
});

➡️ Applies only to tests within that describe block.

Use this when:

• You need scoped setup/reset logic

• You have isolated state per test group

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💡 Pro Tip: Combine Them Smartly

beforeAll(() => startServer()); // once for the file
afterAll(() => stopServer());

describe('User Routes', () => {
  beforeEach(() => seedUserData());
  afterEach(() => clearUserData());

  test('GET /users', () => {});
  test('POST /users', () => {});
});

describe('Auth Routes', () => {
  beforeEach(() => seedAuthData());
  afterEach(() => clearAuthData());

  test('POST /login', () => {});
});

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🧨 Common Mistakes to Avoid

• ❌ Using beforeEach() to connect DB (wastes time)

• ❌ Forgetting afterAll() — leads to hanging tests

• ❌ Global state leakage by skipping afterEach()

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✅ Final Checklist

• beforeAll → Global setup (DB/server start)

• afterAll → Global cleanup (DB/server stop)

• beforeEach → Local per-test reset (mock data)

• afterEach → Cleanup after each test (clear mocks, cookies)

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Use these wisely, and your tests will be faster, isolated, and reliable.