test: add a test moving average decaying even without new data

package.json

@@ -70,6 +70,7 @@
  },
  "devDependencies": {
  "@rollup/plugin-replace": "^2.3.4",
+ "@rollup/plugin-strip": "^2.0.1",
  "@videojs/generator-helpers": "~2.0.1",
  "d3": "^3.4.8",
  "es5-shim": "^4.5.13",

scripts/rollup.config.js

@@ -3,6 +3,7 @@ const worker = require('rollup-plugin-worker-factory');
 const {terser} = require('rollup-plugin-terser');
 const createTestData = require('./create-test-data.js');
 const replace = require('@rollup/plugin-replace');
+const strip = require('@rollup/plugin-strip');
 
 const CI_TEST_TYPE = process.env.CI_TEST_TYPE || '';
 
@@ -57,6 +58,9 @@ const options = {
  }
  defaults.module.unshift('replace');
 
+ defaults.module.unshift('strip');
+ defaults.browser.unshift('strip');
+
  return defaults;
  },
  primedPlugins(defaults) {
@@ -71,6 +75,9 @@ const options = {
  output: {comments: 'some'},
  compress: {passes: 2}
  }),
+ strip: strip({
+ functions: ['TEST_ONLY_*']
+ }),
  createTestData: createTestData()
  });
 

src/playlist-selectors.js

@@ -149,7 +149,7 @@ export const comparePlaylistResolution = function(left, right) {
  * currently detected bandwidth, accounting for some amount of
  * bandwidth variance
  */
-export const simpleSelector = function(
+export let simpleSelector = function(
  master,
  playerBandwidth,
  playerWidth,
@@ -313,6 +313,16 @@ export const simpleSelector = function(
  return null;
 };
 
+export const TEST_ONLY_SIMPLE_SELECTOR = (newSimpleSelector) => {
+ const oldSimpleSelector = simpleSelector;
+
+ simpleSelector = newSimpleSelector;
+
+ return function resetSimpleSelector() {
+ simpleSelector = oldSimpleSelector;
+ };
+};
+
 // Playlist Selectors
 
 /**

test/playlist-selectors.test.js

@@ -1,6 +1,7 @@
 import { module, test } from 'qunit';
 import document from 'global/document';
 import {
+ TEST_ONLY_SIMPLE_SELECTOR,
  simpleSelector,
  movingAverageBandwidthSelector,
  minRebufferMaxBandwidthSelector,
@@ -64,6 +65,50 @@ test('Exponential moving average has a configurable decay parameter', function(a
  assert.equal(playlist.attributes.BANDWIDTH, 50, 'selected the middle playlist');
 });
 
+test('Calling exponential moving average wont decay average unless new bandwidth data was provided', function(assert) {
+ let playlist;
+ const simSel = simpleSelector;
+ const bandwidthAverages = [];
+
+ const resetSimpleSelector = TEST_ONLY_SIMPLE_SELECTOR((...args) => {
+ // second argument to simpleSelector is the average
+ bandwidthAverages.push(args[1]);
+ return simSel(...args);
+ });
+
+ this.vhs.playlists.master.playlists = [
+ { attributes: { BANDWIDTH: 1 } },
+ { attributes: { BANDWIDTH: 50 } },
+ { attributes: { BANDWIDTH: 100 } }
+ ];
+
+ const fiftyPercentDecay = movingAverageBandwidthSelector(0.50);
+
+ this.vhs.systemBandwidth = 50 * Config.BANDWIDTH_VARIANCE + 1;
+ playlist = fiftyPercentDecay.call(this.vhs);
+ assert.equal(playlist.attributes.BANDWIDTH, 50, 'selected the middle playlist');
+
+ this.vhs.systemBandwidth = 1000 * Config.BANDWIDTH_VARIANCE + 1;
+ playlist = fiftyPercentDecay.call(this.vhs);
+ assert.equal(playlist.attributes.BANDWIDTH, 100, 'selected the top playlist');
+
+ // using the systemBandwidth values above, 50->1000
+ // we decay into 1000 after 50 iterations
+ let i = 50;
+
+ while (i--) {
+ playlist = fiftyPercentDecay.call(this.vhs);
+ }
+
+ assert.equal(
+ bandwidthAverages[bandwidthAverages.length - 1],
+ bandwidthAverages[1],
+ 'bandwidth should only change when we get new bandwidth data'
+ );
+
+ resetSimpleSelector();
+});
+
 test(
  'minRebufferMaxBandwidthSelector picks highest rendition without rebuffering',
  function(assert) {