rejectedWith not checking the error message

[mani-vandrangi]

rejectedWith is not returning error when if error message is different from actual value.

Node version: 10.16.3
chai-as-promised version: 7.1.1
chai version: 4.2.0

E.g.: expect(fn()).to.be.rejectedWith(CustomError, error message) is returning always true as long as fn is just throwing custom Error with an error message whose prefix is same as error message.

[siddharthvp]

Having the same issue here.

Code to replicate:

it('test', async () => {
	  function reject42() {
	  	return Promise.reject(42);
	  }
	  await expect(reject42()).to.be.rejectedWith(999);
});

it('test', async () => {
	  function reject42() {
	  	return Promise.reject(42);
	  }
	  await expect(reject42()).to.be.eventually.rejectedWith(999);
});

In both cases test passes rather than fail.

[masterpandabear]

A bit late but I guess this library looks for actual thrown errors for rejected values, for example this fails as expected

    it('test', async () => {
      function reject42 () {
        return Promise.reject(new Error('42'))
      }

      await expect(reject42()).to.eventually.be.rejectedWith('999')
    })

[nilsreichardt]

@masterpandabear But this is only true, if no rejected value is part of the error. Here are some false-positive example:

const mocha = require("mocha");
const chai = require("chai");
const chaiAsPromised = require("chai-as-promised");
chai.use(chaiAsPromised);

it('test 1', async () => {
    function reject42() {
        return Promise.reject(new Error('42'))
    }

    await chai.expect(reject42()).to.eventually.be.rejectedWith('4')
});

it('test 2', async () => {
    function reject42() {
        return Promise.reject(new Error('42'))
    }

    await chai.expect(reject42()).to.eventually.be.rejectedWith('2')
});

Both tests are passing, which is not expected (for me), because it's obvious that 42 != 4 and 42 != 2.

Reproducible source code: https://github.com/nilsreichardt/playground/blob/chai-as-promised-error-message-bug/test/index_test.js

[rmlearney-digicatapult]

This still seems to be the case in mid-2025:

Chai: doesn't like catching a 404 on an async function (equal('') left empty to show actual console message)

    it.only("should return 404 if foo doesn't exist", async () => {
      const response = await foo.bar(a, b)
      expect(response).deep.equal('')
}

         should return 404 if foo doesn't exist:
     Error: http://localhost:8443/foo/ - not found

Chai-as-promised: should catch but doesn't care about matching the error message

      await expect(foo.bar(a, b)).to.be.rejectedWith('http://localhost:8443/foo/ - not found')

Still passes with an empty string:

      await expect(foo.bar(a, b)).to.be.rejectedWith('')