anchor.diff:    print('$clock ELAPSED TIME: $bold${elapsedTime(start)}$reset for $commandDescription in $relativeWorkingDir: ');
   
     if (output != null) {
  -    output.stdout = flattenToString(await savedStdout);
  -    output.stderr = flattenToString(await savedStderr);
  +    output.stdout = _flattenToString(await savedStdout);
  +    output.stderr = _flattenToString(await savedStderr);
     }
   
     // If the test is flaky we don't care about the actual exit.
  
positive.code:   }
  }
  
  T identity<T>(T x) => x;
  
  /// Flattens a nested list of UTF-8 code units into a single string.
  String flattenToString(List<List<int>> chunks) =>
    utf8.decode(chunks.expand<int>(identity).toList(growable: false));
  
  /// Specifies what to do with command output from [runCommand].
  enum OutputMode { print, capture, discard }
  
negative.code:         break;
        case OutputMode.capture:
        case OutputMode.discard:
          stdout.writeln(_flattenToString(await savedStdout));
          stderr.writeln(_flattenToString(await savedStderr));
          break;
      }
      print(
  