WebdriverIO browser.waitUntil proposal

waitUntilTests.js

var assert = require('assert');

const RESOLVE_TIME = 50;
const TIMEOUT = 200;

describe('webdriver.io page', function() {
    it('waitUntil should stop waiting when promise resolves truthy', function () {
        const start = Date.now();
        browser.waitUntil(new Promise((resolve) => {
            setTimeout(() => {
                resolve(true);
            }, RESOLVE_TIME);
        }), TIMEOUT);
        const end = Date.now();
        assert(end - start >= RESOLVE_TIME && end - start < TIMEOUT);
    });

    it('waitUntil should stop waiting when promise resolves falsey', function () {
        const start = Date.now();
        browser.waitUntil(new Promise((resolve) => {
            setTimeout(() => {
                resolve(false);
            }, RESOLVE_TIME);
        }), TIMEOUT);
        const end = Date.now();
        assert(end - start >= RESOLVE_TIME && end - start < TIMEOUT);
    });

    it('waitUntil should stop waiting when promise rejects truthy', function () {
        const start = Date.now();
        browser.waitUntil(new Promise((resolve, reject) => {
            setTimeout(() => {
                reject(true);
            }, RESOLVE_TIME);
        }), TIMEOUT);
        const end = Date.now();
        assert(end - start >= RESOLVE_TIME && end - start < TIMEOUT);
    });

    it('waitUntil should stop waiting when promise rejects falsey', function () {
        const start = Date.now();
        browser.waitUntil(new Promise((resolve, reject) => {
            setTimeout(() => {
                reject(false);
            }, RESOLVE_TIME);
        }), TIMEOUT);
        const end = Date.now();
        assert(end - start >= RESOLVE_TIME && end - start < TIMEOUT);
    });
});

Current results:

․FFF

1 passing (27.90s)
3 failing

1) webdriver.io page waitUntil should stop waiting when promise resolves falsey:
Promise was rejected with the following reason: timeout
running firefox
Error: Promise was rejected with the following reason: timeout
    at waitUntil([object Promise], 8000) - index.js:316:3

2) webdriver.io page waitUntil should stop waiting when promise rejects truthy:
Promise was rejected with the following reason: undefined
running firefox
Error: Promise was rejected with the following reason: undefined
    at waitUntil([object Promise], 8000) - index.js:316:3

3) webdriver.io page waitUntil should stop waiting when promise rejects falsey:
Promise was rejected with the following reason: timeout
running firefox
Error: Promise was rejected with the following reason: timeout
    at waitUntil([object Promise], 8000) - index.js:316:3