From 885a68384b15c43d162fa68b00afb221847b7036 Mon Sep 17 00:00:00 2001
From: yoel-zeldes <yoelz@wix.com>
Date: Sun, 16 Aug 2015 23:45:13 +0300
Subject: [PATCH] add tests to getDistance

---
 lib/similarity.js |   6 +--
 test/test.js      | 102 +++++++++++++++++++++++++++++-----------------
 2 files changed, 67 insertions(+), 41 deletions(-)

diff --git a/lib/similarity.js b/lib/similarity.js
index 7cf112a..5938a4e 100644
--- a/lib/similarity.js
+++ b/lib/similarity.js
@@ -12,7 +12,7 @@ exports.getDistance = function(dataSet, key1, key2) {
 	// get the list of shared_items
 	var sharedItems = {};
 	for (var itemKey in dataSet[key1]) {
-		if (typeof(dataSet[key2][itemKey]) !== 'undefined') {
+		if (dataSet[key2][itemKey] !== undefined) {
 			sharedItems[itemKey] = 1;
 		}
 	}
@@ -25,7 +25,7 @@ exports.getDistance = function(dataSet, key1, key2) {
 	// add up the squares of all the differences
 	var squares = [];
 	for (var itemKey in dataSet[key1]) {
-		if (typeof(dataSet[key2][itemKey]) !== 'undefined') {
+		if (dataSet[key2][itemKey] !== undefined) {
 			var square = Math.pow( dataSet[key1][itemKey] - dataSet[key2][itemKey], 2 );
 			squares.push( square );
 		}
@@ -39,7 +39,7 @@ exports.getPearson = function(dataSet, key1, key2) {
 	// get the list of mutially rated items
 	var sharedItems = {};
 	for (var itemKey in dataSet[key1]) {
-		if (typeof(dataSet[key2][itemKey]) !== 'undefined') {
+		if (dataSet[key2][itemKey] !== undefined) {
 			sharedItems[itemKey] = 1;
 		}
 	}
diff --git a/test/test.js b/test/test.js
index c7d1127..b890b8e 100644
--- a/test/test.js
+++ b/test/test.js
@@ -6,50 +6,45 @@ var similarity = require('../lib/similarity');
 var Recommend = require('../lib/recommend');
 
 
-var getRandomInteger = function(min, max) {
-	return Math.floor( Math.random() * max ) + min;
-};
-
-var getRandomKey = function(dataSet) {
-	var keys = Object.keys(dataSet);
-	var rand = getRandomInteger(0, keys.length);
-	return keys[rand];
-};
-
-
 describe('Recommend', function() {
-	var recommend = undefined;
-	var key = undefined;
-	var key1 = undefined;
-	var key2 = undefined;
-
-	before( function(done) {
-		recommend = new Recommend(dataSet);
-		key = getRandomKey(dataSet);
-		key1 = getRandomKey(dataSet);
-		key2 = getRandomKey(dataSet);
-
-		should.exist(recommend);
-		should.exist(recommend.dataSet);
-		should.exist(recommend.reversedDataSet);
-		should.exist(key);
-		should.exist(key1);
-		should.exist(key2);
-
-		done();
-	});
-
 	describe('similarity', function() {
-		it('#getDistance()', function(done) {
-			var distance = similarity.getDistance(dataSet, key1, key2);
-			should.exist(distance);
-			// console.log( 'similarity.getDistance(dataSet, ' + key1 + ', ' + key2 + ') === ' + distance );
+		function createDataSet() {
+			return Array.prototype.reduce.call(arguments, function addUserToDataSet(dataSet, arg, index) {
+				dataSet[index] = {};
+				arg.forEach(function copyDefinedItems(score, item) {
+					if (score !== undefined) {
+						dataSet[index][item] = score;
+					}
+				});
+				return dataSet;
+			}, {});
+		}
+
+		describe('#getDistance()', function() {
+
+			it('should be 1 for the same user', function () {
+				var distance = similarity.getDistance(createDataSet([1], [1]), 0, 0);
+				should.equal(distance, 1);
+			});
 
-			done();
+			it('should be 0 for users with no shared items', function () {
+				var distance = similarity.getDistance(createDataSet([1, undefined], [undefined, 1]), 0, 1);
+				should.equal(distance, 0);
+			});
+
+			it('should be 1 for users if the shared items have the same score', function () {
+				var distance = similarity.getDistance(createDataSet([1, 1, undefined], [undefined, 1, 3]), 0, 1);
+				should.equal(distance, 1);
+			});
+
+			it('should be 0.5 for users if there is one shared item but the scores differ by 1', function () {
+				var distance = similarity.getDistance(createDataSet([1], [2]), 0, 1);
+				should.equal(distance, 0.5);
+			});
 		});
 
 		it('#getPearson()', function(done) {
-			var pearsonScore = similarity.getPearson(dataSet, key1, key2);
+			var pearsonScore = similarity.getPearson(createDataSet([1], [2]), 0, 1);
 			should.exist(pearsonScore);
 			// console.log( 'similarity.getPearson(dataSet, ' + key1 + ', ' + key2 + ') === ' + pearsonScore );
 
@@ -58,6 +53,37 @@ describe('Recommend', function() {
 	});
 
 	describe('recommend', function() {
+		var recommend = undefined;
+		var key = undefined;
+		var key1 = undefined;
+		var key2 = undefined;
+
+		var getRandomInteger = function(min, max) {
+			return Math.floor( Math.random() * max ) + min;
+		};
+
+		var getRandomKey = function(dataSet) {
+			var keys = Object.keys(dataSet);
+			var rand = getRandomInteger(0, keys.length);
+			return keys[rand];
+		};
+
+		before( function(done) {
+			recommend = new Recommend(dataSet);
+			key = getRandomKey(dataSet);
+			key1 = getRandomKey(dataSet);
+			key2 = getRandomKey(dataSet);
+
+			should.exist(recommend);
+			should.exist(recommend.dataSet);
+			should.exist(recommend.reversedDataSet);
+			should.exist(key);
+			should.exist(key1);
+			should.exist(key2);
+
+			done();
+		});
+
 		it('#getTopMatches()', function(done) {
 			recommend.getTopMatches(key, function(err, topMatches) {
 				should.not.exist(err);