anchor.diff:    /** Which command of [testCase.commands] is currently being executed. */
     int currentStep;
   
  -  static final int kErrorStartingProcess = -171717;  // Chosen arbitrarily.
  -
     RunningProcess(TestCase this.testCase,
         [this.allowRetries = false, this.processQueue]);
   
  
positive.code:    * the actual test and its output is analyzed in [testComplete].
     */
    void stepExitHandler(int exitCode) {
      try {
        process.close();
      } catch (ProcessException e) {
        // If the process is already closed, continue.
      }
      int totalSteps = testCase.commands.length;
      String suffix =' (step $currentStep of $totalSteps)';
      if (currentStep == totalSteps) { // done with test command
  
negative.code:     }
      process = new Process.start(command.executable, command.arguments);
      process.onExit = exitHandler;
      startTime = new Date.now();
      InputStream stdoutStream = process.stdout;
      InputStream stderrStream = process.stderr;
  