Testing Promises & Async/Await in Jest

From the Jest cheat sheet · Async Testing · verified Jul 2026

Testing Promises & Async/Await

Different patterns for testing asynchronous code

javascript

// Using async/await
test('async data fetch', async () => {
  const data = await fetchData()
  expect(data).toBe('data')
})

// Using promises
test('promise resolution', () => {
  return fetchData().then(data => {
    expect(data).toBe('data')
  })
})

// Expect promises
test('resolves/rejects', async () => {
  await expect(fetchData()).resolves.toBe('data')
  await expect(fetchError()).rejects.toThrow('error')
})

// Testing callbacks
test('callback test', (done) => {
  function callback(data) {
    try {
      expect(data).toBe('data')
      done()
    } catch (error) {
      done(error)
    }
  }
  fetchDataCallback(callback)
})

💡 Always return or await promises in tests to avoid false positives

⚡ Use expect.assertions(n) to ensure async assertions run

📌 resolves/rejects matchers make async tests cleaner

🟢 Set custom timeout as third parameter for slow operations

asyncpromises

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