anchor.diff:                    expect(target[i], source[i - shift]);
                   }
                 }
  -              expect(() => source << -1 - shift, throwsArgumentError);
               }
  +            expect(() => source << -1, throwsArgumentError);
             }
           });
           test('shift-right', () {
  
positive.code:         });
          test('writing', () {
            for (var len = 0; len < 100; len++) {
              var source = randomBools(389 * len, len);
              var target = new BitList(len);
              expect(() => target[-1] = true, throwsRangeError);
              for (var i = 0; i < len; i++) {
  
negative.code:                   expect(target[i], source[i + shift]);
                  }
                }
              }
              expect(() => source << -1, throwsArgumentError);
            }
          });
        });
  