Stress test using Selenium JavaScript webdriver

stress.js

const { exec } = require("child_process")
const { Builder } = require("selenium-webdriver")

/**
 * Instance a stress test
 * @param {String<URL>} url The URL to stress test 
 * @param {Integer} numWorkers The number of workers to instance in the test
 * @param {String} browser The browser to use for the test (requires driver in path)
 * @param {Boolean} stopImmediately Whether to stop the test immediately after finishing
 * @example <caption>Stress test with 100 workers using Chrome and immediate stopping</caption>
 * const stressTest = new StressTest("http://some/url/", 100, "chrome", true)
 * stressTest.run()
 * @example <caption>Stress test with 20 workers using Firefox</caption>
 * const stressTest = new StressTest("http://some/url/", 20, "firefox", false)
 * stressTest.run()
 */
class StressTest {
    constructor (url, numWorkers, browser, stopImmediately=true) {
        this.url = url
        this.numWorkers = numWorkers
        this.browser = browser ? browser : "chrome"
        this.stopImmediately = stopImmediately
    }

    loadURL (i) {
        return new Promise((resolve, reject) => {
            let driver = new Builder().forBrowser(this.browser).build()
            console.time(`Worker #${i + 1}`)
            driver.get(this.url).then(() => {
                resolve({ i, driver })
            })
        })
    }

    startWorkers () {
        return new Promise((resolve, reject) => {
            let c = 0
            for (let i = 0; i < this.numWorkers; i++) {
                this.loadURL(i)
                    .then((result) => {
                        c++
                        console.timeEnd(`Worker #${result.i + 1}`)
                        if (this.stopImmediately) result.driver.quit()
                        if (c === this.numWorkers) {
                            resolve(this.numWorkers)
                        }
                    })
            }
        })
    }

    killAll () {
        exec("pkill chromedriver")
        exec("pkill chromium-browse")
    }

    run () {
        return new Promise((resolve, reject) => {
            this.startWorkers().then((numWorkers) => {
                console.log(`Finished stress test with ${this.numWorkers} worker${this.numWorkers > 1 ? "s" : ""}.`)
            })
        })
    }

}