How can I check the type of the error thrown asyncronously in Jest?

Question

Suppose I have a function like this:

const f = async () => {
  throw new Error('Huh???!');
};

And I want to test that it throws a RangeError (not just an Error) using Jest.

test('f throws a RangeError', () => {
  expect(f()).rejects.toThrowError(RangeError);
});

However this test passes.

How can I check the type of the error thrown asyncronously in Jest?

I don't know if I'm right but you may try to `await f()` within a try/catch and in the catch check the `typeof` the error. — Striped, Feb 02 '18 at 10:53
That is one option, but `rejects` is meant to do the `await`ing — sdgfsdh, Feb 02 '18 at 10:56
I just found that https://stackoverflow.com/q/46042613/1985912. — Striped, Feb 02 '18 at 11:04

score 2 · Accepted Answer · answered Feb 02 '18 at 11:28

2

You can use the toBeInstanceOf matcher after rejects:

test('f throws a RangeError', () => {
  expect(f()).rejects.toBeInstanceOf(RangeError);
});

answered Feb 02 '18 at 11:28

sdgfsdh

1 Answers1