A/B test bucketing wrapper for page issues AB.

Provides a class that initiates AB-test bucketing and registers
as a MF module. Activates the reading depth test for users who are bucketed
in either buckets "A" or "B".

Does not add event-logging or visual style changes for page issues AB test.

Bug: T193584
Change-Id: If8504a35059c6d1b056cef063a595b1c2ffd351a

includes/MinervaHooks.php

@@ -73,7 +73,9 @@ class MinervaHooks {
 		$testModule = [
 			'dependencies' => [
 				'mobile.startup',
-				'skins.minerva.notifications.badge'
+				'skins.minerva.notifications.badge',
+				'mediawiki.user',
+				'mediawiki.experiments'
 			],
 			'localBasePath' => dirname( __DIR__ ),
 			'remoteSkinPath' => 'MinervaNeue',
@@ -82,9 +84,11 @@ class MinervaHooks {
 				// additional scaffolding (minus initialisation scripts)
 				'resources/skins.minerva.scripts/utils.js',
 				'resources/skins.minerva.scripts/DownloadIcon.js',
+				'resources/skins.minerva.scripts/AB.js',
 				// test files
 				'tests/qunit/skins.minerva.scripts/test_DownloadIcon.js',
 				'tests/qunit/skins.minerva.scripts/test_utils.js',
+				'tests/qunit/skins.minerva.scripts/test_AB.js',
 				'tests/qunit/skins.minerva.notifications.badge/test_NotificationBadge.js'
 			],
 		];

resources/skins.minerva.scripts/AB.js

@@ -0,0 +1,78 @@
+/*
+ * Bucketing wrapper for creating AB-tests.
+ *
+ * Given a test name, sampling rate, and session ID, provides a class
+ * that buckets users into predefined bucket ("control", "A", "B") and
+ * starts an AB-test.
+ */
+
+( function ( mw, M, mwExperiments ) {
+
+	/**
+	 * Buckets users based on params and exposes an `isEnabled` and `getBucket` method.
+	 *
+	 * @param {string} testName name of the AB-test.
+	 * @param {number} samplingRate sampling rate for the AB-test.
+	 * @param {number} sessionId session ID for user bucketing.
+	 * @constructor
+	 */
+	function AB( testName, samplingRate, sessionId ) {
+
+		var CONTROL_BUCKET = 'control',
+			test = {
+				name: testName,
+				enabled: !!samplingRate,
+				buckets: {
+					control: 1 - samplingRate,
+					A: samplingRate / 2,
+					B: samplingRate / 2
+				}
+			};
+		/**
+		 * Starts the AB-test and enters the user into the Reading Depth test.
+ 		 */
+		function startABTest() {
+			// See: https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/WikimediaEvents/+/437686/
+			mw.track( 'wikimedia.event.ReadingDepthSchema.enable' );
+		}
+
+		/**
+		 * Gets the users AB-test bucket
+		 *
+		 * @return {string} AB-test bucket, CONTROL_BUCKET by default, "A" or "B" buckets otherwise.
+		 */
+		function getBucket() {
+			return mwExperiments.getBucket( test, sessionId );
+		}
+
+		/**
+		 * Checks whether or not a user is in the AB-test,
+		 *
+		 * @return {boolean}
+		 */
+		function isEnabled() {
+			return getBucket() !== CONTROL_BUCKET;
+		}
+
+		/**
+		 * Initiates the AB-test.
+		 *
+		 * return {void}
+		 */
+		function init() {
+			if ( isEnabled() ) {
+				startABTest();
+			}
+		}
+
+		init();
+
+		return {
+			getBucket: getBucket,
+			isEnabled: isEnabled
+		};
+	}
+
+	M.define( 'skins.minerva.scripts/AB', AB );
+
+}( mw, mw.mobileFrontend, mw.experiments ) );

skin.json

@@ -328,7 +328,10 @@
 				"mobile.issues",
 				"mobile.search.api",
 				"mobile.search",
-				"mobile.references"
+				"mobile.references",
+				"mediawiki.user",
+				"mediawiki.storage",
+				"mediawiki.experiments"
 			],
 			"messages": [
 				"edithelp",
@@ -355,6 +358,7 @@
 				"resources/skins.minerva.scripts/search.js",
 				"resources/skins.minerva.scripts/references.js",
 				"resources/skins.minerva.scripts/utils.js",
+				"resources/skins.minerva.scripts/AB.js",
 				"resources/skins.minerva.scripts/cleanuptemplates.js"
 			]
 		},

tests/qunit/skins.minerva.scripts/test_AB.js

@@ -0,0 +1,40 @@
+( function ( M ) {
+
+	var AB = M.require( 'skins.minerva.scripts/AB' ),
+		aBName = 'WME.MinervaABTest',
+		samplingRate = 0.5;
+
+	QUnit.module( 'Minerva AB-test' );
+
+	QUnit.test( 'Bucketing test', function ( assert ) {
+		var userBuckets = {
+				control: 0,
+				A: 0,
+				B: 0
+			},
+			maxUsers = 1000,
+			bucketingTest,
+			i;
+
+		for ( i = 0; i < maxUsers; i++ ) {
+			bucketingTest = new AB( aBName, samplingRate, mw.user.generateRandomSessionId() );
+			userBuckets[ bucketingTest.getBucket() ] += 1;
+		}
+
+		assert.strictEqual(
+			( userBuckets.control / maxUsers > 0.4 ) &&
+			( userBuckets.control / maxUsers < 0.6 ),
+			true, 'test control group is about 50% (' + userBuckets.control / 10 + '%)' );
+
+		assert.strictEqual(
+			( userBuckets.A / maxUsers > 0.2 ) &&
+			( userBuckets.A / maxUsers < 0.3 ),
+			true, 'test group A is about 25% (' + userBuckets.A / 10 + '%)' );
+
+		assert.strictEqual(
+			( userBuckets.B / maxUsers > 0.2 ) &&
+			( userBuckets.B / maxUsers < 0.3 ),
+			true, 'test group B is about 25% (' + userBuckets.B / 10 + '%)' );
+	} );
+
+}( mw.mobileFrontend ) );