How to test a nested error thrown from an async function?

Question

Consider the following functions

const aPrivateAsyncQuery = async () => {
  try {
    return await axios.post('someURL', {query: 'someQuery'})
  } catch (error) {
    throw new Error(`A thrown error: ${error}`)
  }
}

export const aPublicAsyncFunction = async someVariable => {
  const data = await aPrivateAsyncQuery()
  if (data[someVariable]){
    return data[someVariable]
  }
  return {}
}

---

How can one test that aPrivateAsyncQuery throws an error when aPublicAsyncFunction is called?

I currently have the following test... which mentions that no throw happened.

  it('should throw when nested function throws', async () => {
    const someVariable = 'foo'

    axios.post.mockRejectedValue(new Error('bar'))

    expect(async () => { await aPublicAsyncFunction(someVariable) }).toThrow()
  })

Thanks in advance!

---

EDIT

The following implementation worked perfectly:

  it('should throw when nested function throws', async () => {
    const someVariable = 'foo'

    axios.post.mockRejectedValue(new Error('bar'))

    await expect(aPublicAsyncFunction(someVariable)).rejects.toThrowError('bar')
  })

Answer 1

It seems that expect toThrow is not very well supported with async functions .

As per that issue, you can test your method with the syntax:

it('should throw when nested function throws', async () => {
    const someVariable = 'foo'

    jest.spyOn(axios, 'post')
        .mockImplementation(() => Promise.reject(new Error('bar')));

    await expect(aPublicAsyncFunction(someVariable)).rejects.toThrow(new Error('A thrown error: Error: bar'));
});