docs(q): added testing information

Author: mhevery

src/ng/q.js

@@ -123,6 +123,30 @@
  *   you can treat promises attached to a scope as if they were the resulting values.
  * - Q has many more features that $q, but that comes at a cost of bytes. $q is tiny, but contains
  *   all the important functionality needed for common async tasks.
+ * 
+ *  # Testing
+ * 
+ *  <pre>
+ *    it('should simulate promise', inject(function($q, $rootSCope) {
+ *      var deferred = $q.defer();
+ *      var promise = deferred.promise;
+ *      var resolvedValue;
+ * 
+ *      promise.then(function(value) { resolvedValue = value; });
+ *      expect(resolvedValue).toBeUndefined();
+ * 
+ *      // Simulate resolving of promise
+ *      defered.resolve(123);
+ *      // Note that the 'then' function does not get called synchronously.
+ *      // This is because we want the promise API to always be async, whether or not
+ *      // it got called synchronously or asynchronously.
+ *      expect(resolvedValue).toBeUndefined();
+ * 
+ *      // Propagate promise resolution to 'then' functions using $apply().
+ *      $rootScope.$apply();
+ *      expect(resolvedValue).toEqual(123);
+ *    });
+ *  </pre>
  */
 function $QProvider() {