feat: add mocked timer detection and try to workaround them

src/browser.js

@@ -2,8 +2,16 @@ import Hookable from 'hable'
 import onExit from 'signal-exit'
 import BrowserError from './utils/error'
 import Xvfb from './utils/commands/xvfb'
-import { abstractGuard, loadDependency, getBrowserConfigFromString, getBrowserImportFromConfig } from './utils'
 import { browsers } from './browsers'
+import {
+  abstractGuard,
+  loadDependency,
+  isMockedFunction,
+  disableTimers,
+  enableTimers,
+  getBrowserConfigFromString,
+  getBrowserImportFromConfig
+} from './utils'
 
 export default class Browser extends Hookable {
   constructor(config = {}) {
@@ -58,6 +66,16 @@ export default class Browser extends Hookable {
     if (this.config.xvfb !== false) {
       Xvfb.load(this)
     }
+
+    if (isMockedFunction(setTimeout, 'setTimeout')) {
+      // eslint-disable-next-line no-console
+      console.warn(`Mocked timers detected
+
+The browser probably won't ever start with globally mocked timers. Will try to automatically use real timers on start and set to use fake timers after start. If the browser still hangs and doesn't start, make sure to only mock the global timers after the browser has started `)
+
+      this.hook('start:before', () => enableTimers())
+      this.hook('start:after', () => disableTimers())
+    }
   }
 
   static async get(browserString = '', config = {}) {

src/utils/index.js

@@ -10,7 +10,23 @@ export function abstractGuard(className, { name } = {}) {
   }
 }
 
+export function isMockedFunction(fn, fnName) {
+  return fn.name !== fnName
+}
+
 // TODO: add more test framework checks like sinon?
+export function disableTimers() {
+  // find Jest fingerprint
+  if (process.env.JEST_WORKER_ID) {
+    try {
+      jest.useFakeTimers()
+    } catch (e) {
+      /* istanbul ignore next */
+      throw new BrowserError(`Enabling fake timers failed: ${e.message}`)
+    }
+  }
+}
+
 export function enableTimers() {
   // find Jest fingerprint
   if (process.env.JEST_WORKER_ID) {
@@ -86,9 +102,9 @@ export function getDefaultHtmlCompiler() {
   return html => compile(html).ast
 }
 
-export async function loadDependency(dependency) {
+export function loadDependency(dependency) {
   try {
-    return await import(dependency).then(m => m.default || m)
+    return import(dependency).then(m => m.default || m)
   } catch (e) {
     throw new BrowserError(`Could not import the required dependency '${dependency}'
 (error: ${e.message})