Adding isNotEmpty property to collection and string.

tests/corelib/queue_test.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library queue.test;
 
 import "package:expect/expect.dart";
 import 'dart:collection';
 
 abstract class QueueTest {
@@ skipping 106 matching lines @@
     Expect.equals(255, queue.removeFirst());
     Expect.isTrue(queue.isEmpty);
 
     testAddAll();
     testLengthChanges();
     testLarge();
     testFromListToList();
   }
 
   void checkQueue(Queue queue, int expectedSize, int expectedSum) {
-    Expect.equals(expectedSize, queue.length);
+    testLength(expectedSize, queue);
     int sum = 0;
     void sumElements(int value) {
       sum += value;
     }
     queue.forEach(sumElements);
     Expect.equals(expectedSum, sum);
   }
 
   testLength(int length, Queue queue) {
     Expect.equals(length, queue.length);
     ((length == 0) ? Expect.isTrue : Expect.isFalse)(queue.isEmpty);
+    ((length != 0) ? Expect.isTrue : Expect.isFalse)(queue.isNotEmpty);
   }
 
   void testAddAll() {
     Set<int> set = new Set<int>.from([1, 2, 4]);
     Expect.equals(3, set.length);
 
     Queue queue1 = newQueueFrom(set);
     Queue queue2 = newQueue();
     Queue queue3 = newQueue();
     testLength(3, queue1);
@@ skipping 251 matching lines @@
     }
     Expect.equals(null, entry2);
   }
 }
 
 
 main() {
   new DoubleLinkedQueueTest().testMain();
   new ListQueueTest().testMain();
 }