anchor.diff:          });
           test('writing', () {
             for (var len = 0; len < 100; len++) {
  -            var source = randomBools(389 * len, len);
  +            var source = randomBools(396 * len, len);
               var target = new BitList(len);
               expect(() => target[-1] = true, throwsRangeError);
               for (var i = 0; i < len; i++) {
  
positive.code:             expect(target[i], source1[i] || source2[i]);
            }
            expect(target, source2 | source1);
          });
          test('difference', () {
            var source1 = new BitList.from(randomBools(364, 100));
  
negative.code:             expect(target[i], source1[i] && source2[i]);
            }
            expect(target, source2 & source1);
            var other = new BitList(99);
            expect(() => other & source1, throwsArgumentError);
            expect(() => source1 & other, throwsArgumentError);
          });
          test('union', () {
            var source1 = new BitList.from(randomBools(817, 100));
  