javascript - Can you write async tests that expect toThrow?

Question

I'm writing an async test that expects the async function to throw like this:

it("expects to have failed", async () => {
  let getBadResults = async () => {
    await failingAsyncTest()
  }
  expect(await getBadResults()).toThrow()
})

But jest is just failing instead of passing the test:

 FAIL  src/failing-test.spec.js
  ● expects to have failed

    Failed: I should fail!

If I rewrite the test to looks like this:

expect(async () => {
  await failingAsyncTest()
}).toThrow()

I get this error instead of a passing test:

expect(function).toThrow(undefined)

Expected the function to throw an error.
But it didn't throw anything.

Answer 1

You can test your async function like this:

it('should test async errors', async () =>  {        
    await expect(failingAsyncTest())
    .rejects
    .toThrow('I should fail');
});

'I should fail' string will match any part of the error thrown.