E2e jsdom fix (#1470)

* E2E: run tests when react is ready

* Entangle e2e with callbacks

* Remove unused e2e lines

packages/react-scripts/fixtures/kitchensink/integration/initDOM.js

@@ -5,9 +5,6 @@ const path = require('path')
 
 let getMarkup
 let resourceLoader
-// this value could be tweaked in order to let the resource
-// retriever get every file and jsdom execute react
-let timeToWaitForJsToExecute
 
 if (process.env.E2E_FILE) {
   const file = path.isAbsolute(process.env.E2E_FILE)
@@ -21,8 +18,6 @@ if (process.env.E2E_FILE) {
     null,
     fs.readFileSync(path.join(path.dirname(file), resource.url.pathname), 'utf8')
   )
-
-  timeToWaitForJsToExecute = 0
 } else if (process.env.E2E_URL) {
   getMarkup = () => new Promise(resolve => {
     http.get(process.env.E2E_URL, (res) => {
@@ -32,11 +27,7 @@ if (process.env.E2E_FILE) {
     })
   })
 
-  resourceLoader = (resource, callback) => {
-    return resource.defaultFetch(callback)
-  }
-
-  timeToWaitForJsToExecute = 100
+  resourceLoader = (resource, callback) => resource.defaultFetch(callback)
 } else {
   it.only('can run jsdom (at least one of "E2E_FILE" or "E2E_URL" environment variables must be provided)', () => {
     expect(new Error('This isn\'t the error you are looking for.')).toBeUndefined()
@@ -47,16 +38,16 @@ export default feature => new Promise(async resolve => {
   const markup = await getMarkup()
   const host = process.env.E2E_URL || 'http://localhost:3000'
   const doc = jsdom.jsdom(markup, {
-    features : {
-      FetchExternalResources : ['script', 'css'],
-      ProcessExternalResources : ['script'],
+    features: {
+      FetchExternalResources: ['script', 'css'],
+      ProcessExternalResources: ['script'],
     },
+    created: (_, win) => win.addEventListener('ReactFeatureDidMount', () => resolve(doc), true),
+    deferClose: true,
     resourceLoader,
     url: `${host}#${feature}`,
     virtualConsole: jsdom.createVirtualConsole().sendTo(console),
   })
 
-  doc.defaultView.addEventListener('load', () => {
-    setTimeout(() => resolve(doc), timeToWaitForJsToExecute)
-  }, false)
+  doc.close()
 })