[BUGFIX beta] Add cache tests and fix undefined value

Author: mmun

packages/ember-metal/lib/cache.js

@@ -37,7 +37,7 @@ Cache.prototype = {
       value = this.set(key, this.func(key));
     } else if (value === UNDEFINED) {
       this.hits ++;
-      value = UNDEFINED;
+      value = undefined;
     } else {
       this.hits ++;
       // nothing to translate

packages/ember-metal/tests/cache_test.js

@@ -0,0 +1,52 @@
+import Cache from "ember-metal/cache";
+
+QUnit.module("Cache");
+
+test("basic", function() {
+  var cache = new Cache(100, function(key) {
+    return key.toUpperCase();
+  });
+
+  equal(cache.get("foo"), "FOO");
+  equal(cache.get("bar"), "BAR");
+  equal(cache.get("foo"), "FOO");
+});
+
+test("caches computation correctly", function() {
+  var count = 0;
+  var cache = new Cache(100, function(key) {
+    count++;
+    return key.toUpperCase();
+  });
+
+  equal(count, 0);
+  cache.get("foo");
+  equal(count, 1);
+  cache.get("bar");
+  equal(count, 2);
+  cache.get("bar");
+  equal(count, 2);
+  cache.get("foo");
+  equal(count, 2);
+});
+
+test("handles undefined value correctly", function() {
+  var cache = new Cache(100, function(key) {});
+
+  equal(cache.get("foo"), undefined);
+});
+
+test("continues working after reaching cache limit", function() {
+  var cache = new Cache(3, function(key) {
+    return key.toUpperCase();
+  });
+
+  cache.get("a");
+  cache.get("b");
+  cache.get("c");
+
+  equal(cache.get("d"), "D");
+  equal(cache.get("a"), "A");
+  equal(cache.get("b"), "B");
+  equal(cache.get("c"), "C");
+});