anchor.diff:      _taskBeforeEnd = currentSchedule.tasks.contents.last;
       schedule(() {
         _endExpected = true;
  -      return _process.then((p) => p.kill()).then((_) => _exitCode);
  +      return _process
  +          .then((p) => p.kill(ProcessSignal.SIGKILL))
  +          .then((_) => _exitCode);
       }, "waiting for process '$description' to die");
     }
   
  
positive.code: /// synchronously. All operations on this class are scheduled.
  ///
  /// Before running the test, either [shouldExit] or [kill] must be called on
  /// this to ensure that the process terminates when expected.
  ///
  /// If the test fails, this will automatically print out any stdout and stderr
  /// from the process to aid debugging.
  
negative.code:       if (!_exitCode.hasValue) {
          killedPrematurely = true;
          _endExpected = true;
          _process.value.kill(ProcessSignal.SIGKILL);
          // Ensure that the onException queue waits for the process to actually
          // exit after being killed.
          wrapFuture(_process.value.exitCode, "waiting for process "
  