test: add basic memory leak test (#1650)

* test: add basic memory leak test

* try to fix test

src/routes/_utils/delegate.js

@@ -2,8 +2,8 @@
 
 const callbacks = {}
 
-if (process.browser && process.env.NODE_ENV !== 'production') {
-  window.delegateCallbacks = callbacks
+if (process.browser) {
+  window.__delegateCallbacks = callbacks
 }
 
 function onEvent (e) {

src/routes/_utils/eventBus.js

@@ -2,8 +2,8 @@ import EventEmitter from 'events-light'
 
 export const eventBus = new EventEmitter()
 
-if (process.browser && process.env.NODE_ENV !== 'production') {
-  window.eventBus = eventBus
+if (process.browser) {
+  window.__eventBus = eventBus
 }
 
 export function on (eventName, component, method) {

src/routes/_utils/resize.js

@@ -4,8 +4,8 @@ const DEBOUNCE_DELAY = 700
 
 const listeners = new Set()
 
-if (process.browser && process.env.NODE_ENV !== 'production') {
-  window.resizeListeners = listeners
+if (process.browser) {
+  window.__resizeListeners = listeners
 }
 
 if (process.browser) {

tests/spec/038-memory-leaks.js

@@ -0,0 +1,46 @@
+import {
+  composeInput,
+  getNthAutosuggestionResult,
+  getNumSyntheticListeners,
+  getUrl,
+  homeNavButton,
+  scrollToStatus,
+  scrollToTop,
+  settingsNavButton, sleep
+} from '../utils'
+import { loginAsFoobar } from '../roles'
+
+fixture`038-memory-leaks.js`
+  .page`http://localhost:4002`
+
+async function goToStartPoint (t) {
+  await t
+    .click(settingsNavButton)
+    .expect(getUrl()).contains('/settings')
+}
+
+async function interactAndGoToEndPoint (t) {
+  await t
+    .click(homeNavButton)
+    .expect(getUrl()).eql('http://localhost:4002/')
+  await scrollToStatus(t, 15)
+  await scrollToTop()
+  await t
+    .typeText(composeInput, 'hey @qu')
+    .expect(getNthAutosuggestionResult(1).find('.sr-only').innerText).contains('@quux')
+    .click(settingsNavButton)
+    .expect(getUrl()).contains('/settings')
+}
+
+test('Does not leak synthetic listeners', async t => {
+  await loginAsFoobar(t)
+  await goToStartPoint(t)
+  await sleep(1000)
+  const numSyntheticListeners = await getNumSyntheticListeners()
+  await t
+    .expect(numSyntheticListeners).typeOf('number')
+  await interactAndGoToEndPoint(t)
+  await sleep(1000)
+  await t
+    .expect(getNumSyntheticListeners()).eql(numSyntheticListeners)
+})

tests/utils.js

@@ -119,6 +119,13 @@ export const sleep = timeout => new Promise(resolve => setTimeout(resolve, timeo
 
 export const getUrl = exec(() => window.location.href)
 
+export const getNumSyntheticListeners = exec(() => {
+  return Object.keys(window.__eventBus.$e).map(key => window.__eventBus.listenerCount(key))
+    .concat(window.__resizeListeners.size)
+    .concat(Object.keys(window.__delegateCallbacks).length)
+    .reduce((a, b) => a + b, 0)
+})
+
 export const getMediaScrollLeft = exec(() => document.querySelector('.media-scroll').scrollLeft || 0)
 
 export const getActiveElementClassList = exec(() =>