anchor.diff:              differ.toString(),
               iterableChangesAsString(
                   collection: ["a", "boo"], previous: ["a", "boo"]));
  -      });
  -      test("should ignore [NaN] != [NaN] (JS)", () {
  -        var l = [double.NAN];
  -        differ.check(l);
  -        differ.check(l);
  -        expect(
  -            differ.toString(),
  -            iterableChangesAsString(
  -                collection: [double.NAN], previous: [double.NAN]));
         });
         test("should remove and add same item", () {
           var l = ["a", "b", "c"];
  
positive.code: import 'dart:collection';
  
  import 'package:test/test.dart';
  import 'package:_tests/test_util.dart';
  import 'package:angular/src/core/change_detection/differs/default_iterable_differ.dart';
  
  void main() {
  
negative.code:     });
      group("trackBy function by index", () {
        var differ;
        var trackByIndex = (int index, Object item) => index;
        setUp(() {
          differ = new DefaultIterableDiffer(trackByIndex);
        });
  