Writing Unit Tests with Jest

What testing pattern is shown for Promise-based operations?

test('async operation completes', async () => {
  await expect(fetchData()).resolves.toEqual({ data: 'value' });
  await expect(failingFetch()).rejects.toThrow('Error');
});

Callback testing
Event testing
Promise resolution testing
This demonstrates Promise testing patterns: 1) Tests both successful and failed Promise resolutions, 2) Uses async/await for cleaner test code, 3) Verifies Promise fulfillment values, 4) Checks Promise rejection scenarios, 5) Handles asynchronous operations properly, 6) Maintains clear test intentions, 7) Essential for testing modern async code, 8) Improves async test reliability.
Timer testing

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