anchor.diff:            expect(target.values, [2, 3, 4]);
           });
           test('iterables', () {
  -          var target = new BiMap.fromIterables(example.keys, example.values);
  -          expect(target.keys, [1, 2, 3]);
  -          expect(target.values, ['a', 'b', 'c']);
  -          target = new BiMap.fromIterables(example.values, example.keys);
  -          expect(target.keys, ['a', 'b', 'c']);
  -          expect(target.values, [1, 2, 3]);
  +          var target1 = new BiMap.fromIterables(example.keys, example.values);
  +          expect(target1.keys, [1, 2, 3]);
  +          expect(target1.values, ['a', 'b', 'c']);
  +          var target2 = new BiMap.fromIterables(example.values, example.keys);
  +          expect(target2.keys, ['a', 'b', 'c']);
  +          expect(target2.values, [1, 2, 3]);
           });
           test('iterables (error)', () {
             expect(() => new BiMap.fromIterables([1], []), throwsArgumentError);
  
positive.code:         });
          test('define if absent', () {
            var target = new BiMap.from(example);
            target.putIfAbsent(1, () => fail('Value already present!'));
            target.putIfAbsent(4, () => 'd');
            expect(target[4], 'd');
          });
  
negative.code:         test('invalid', () {
            var set = new Multiset.from(['a', 'a', 'b', 'b', 'b']);
            expect(() => set.remove('c'), returnsNormally);
            expect(() => set.remove('z'), returnsNormally);
            expect(set, isNot(isEmpty));
            expect(set, hasLength(5));
            expect(set, unorderedEquals(['a', 'a', 'b', 'b', 'b']));
  