Put time limit on Jest test?

Question

I'm running a set of tests with Jest to demonstrate Big O using two different methods for Fibonacci.

const fastFib = require('./../fastFib');
const slowFib = require('./../slowFib');

test('Fast way of getting Fibonacci of 44', () => {
  expect(fastFib(44)).toBe(701408733);
});

test('Slow way of getting Fibonacci of 44', () => {
  expect(slowFib(44)).toBe(701408733);
});

I'm wondering if there is a way to specify the maximum length of a test? I saw you can pass a third variable for an async timeout but it doesn't seem to have any effect on normal functions:

test('Slow way of getting Fibonacci of 44', () => {
  expect(slowFib(44)).toBe(701408733);
}, 5000);

Is there a way I can specify the maximum execution time for a function with Jest?

---

I will share slowFib.js for reference:

function fib(n) {
  return (n<=1) ? n : fib(n - 1) + fib(n - 2);
}

module.exports = fib;

Answer 1

so your test pauses because of sync execution - there is no way to interrupt that by timeout. You need to "split execution". Next version fails to me:

test('Slow way of getting Fibonacci of 44', (done) => {
  expect(slowFib(44)).toBe(701408733);
  setTimeout(done, 10); // smallest timeout possible to make different macrotask
}, 5000);

PS I also believe this should be achievable by marking test async but have not yet figured how exactly.

[UPD] you actually may achieve your goal without using test's timeout:

test('Slow way of getting Fibonacci of 44', () => {
  const start = new Date();
  expect(slowFib(44)).toBe(701408733);
  expect(new Date() - start).toBeLessThan(5000);
});

Answer 2

In your test file you can set jest.setTimeout(5000); which overrides the default timeout for a test case in jest