more tests for collection, 0 is a valid id.

test/collection.js

@@ -2,18 +2,45 @@ $(document).ready(function() {
 
   module("Backbone collections");
 
-  test("collections: simple", function() {
-    a = new Backbone.Model({label: 'a'});
-    b = new Backbone.Model({label: 'b'});
-    c = new Backbone.Model({label: 'c'});
-    d = new Backbone.Model({label: 'd'});
-    col = new Backbone.Collection([a,b,c,d]);
+  var a = new Backbone.Model({id: 4, label: 'a'});
+  var b = new Backbone.Model({id: 3, label: 'b'});
+  var c = new Backbone.Model({id: 2, label: 'c'});
+  var d = new Backbone.Model({id: 1, label: 'd'});
+  var col = new Backbone.Collection([a,b,c,d]);
+
+  test("collections: simple and sorted", function() {
     equals(col.first(), a, "a should be first");
     equals(col.last(), d, "d should be last");
+    col.comparator = function(model) { return model.id; };
+    col.sort();
+    equals(col.first(), d, "d should be first");
+    equals(col.last(), a, "a should be last");
+    equals(col.length, 4);
   });
 
-  test("collections: sorted", function() {
+  test("collections: get, getByCid", function() {
+    equals(col.get(1), d);
+    equals(col.get(3), b);
+    equals(col.getByCid(col.first().cid), col.first());
+  });
 
+  test("collections: getIds, getCids", function() {
+    equals(col.getIds().sort().join(' '), '1 2 3 4');
+    equals(col.getCids().sort().join(' '), 'c1 c2 c3 c4');
+  });
+
+  test("collections: at", function() {
+    equals(col.at(2), b);
+  });
+
+  test("collections: add", function() {
+    var added = null;
+    col.bind('add', function(model){ added = model.get('label'); });
+    var e = new Backbone.Model({id: 0, label : 'e'});
+    col.add(e);
+    equals(added, 'e');
+    equals(col.length, 5);
+    equals(col.first(), e);
   });
 
 });