Writing Unit Tests with Jest

What test setup pattern is being used?

describe('API client', () => {
  let client;
  
  beforeEach(() => {
    client = new ApiClient();
    jest.spyOn(client, 'request');
  });
  
  afterEach(() => {
    jest.restoreAllMocks();
  });

Global setup
Module setup
Instance setup
This demonstrates proper instance setup pattern: 1) Creates fresh instance per test, 2) Initializes spies consistently, 3) Cleans up after each test, 4) Maintains test isolation, 5) Prevents test interference, 6) Follows AAA pattern setup, 7) Common for class testing, 8) Ensures reliable test state.
Mock setup

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