Testing promise with mocha & chai as promised

index.js

const chai = require('chai');
const expect = chai.expect;
const chaiAsPromised = require('chai-as-promised');

const index = require('../index.js');

chai.use(chaiAsPromised);

describe('Function foo', () => {
    it('should accpet anything but one', () => {
        const promise = index.foo(0);
        return expect(promise).to.eventually.equal(0);
    });

    it('should throw error is apply one', () => {
        const promise = index.foo(1);
       // return expect(promise).to.be.rejected;
        return expect(promise).to.be.rejectedWith('Found an error');
    })
});