Modify .extend to copy the parent's constructor

spec/javascripts/rosie.spec.js

@@ -47,11 +47,28 @@ describe('Factory', function() {
   });
 
   describe('extend', function() {
+    var Thing = function(attrs) {
+      for(var attr in attrs) {
+        this[attr] = attrs[attr];
+      }
+    };
+    var Thingy = function(attrs) {
+      for(var attr in attrs) {
+        this[attr] = attrs[attr];
+      }
+    };
+
     beforeEach(function() {
-      Factory.define('thing').attr('name', 'Thing 1').after(function(obj) {
+      Factory.define('thing', Thing).attr('name', 'Thing 1').after(function(obj) {
         obj.afterCalled = true;
       });
       Factory.define('anotherThing').extend('thing').attr('title', 'Title 1');
+      Factory.define('differentThing', Thingy).extend('thing').attr('title', 'Title 1');
+    });
+
+    it('should extend the constructor', function() {
+      expect(Factory.build('anotherThing') instanceof Thing).toBe(true);
+      expect(Factory.build('differentThing') instanceof Thingy).toBe(true);
     });
 
     it('should extend attributes', function() {

src/rosie.js

@@ -44,6 +44,8 @@ Factory.prototype = {
 
   extend: function(name) {
     var factory = Factory.factories[name];
+    // Copy the parent's constructor
+    if (this.construct === undefined) { this.construct = factory.construct; }
     for(var attr in factory.attrs) {
       if(factory.attrs.hasOwnProperty(attr)) {
         this.attrs[attr] = factory.attrs[attr];