stderr:
Unhandled exception:
type 'Null' is not a subtype of type 'bool' of 'boolean expression'.
 0. Function: 'RunningProcess.testComplete' url: 'file:///e:/b/build/slave/vm-win32-release/build/dart/tools/testing/dart/test_runner.dart' line:551 col:67
 1. Function: 'RunningProcess.stepExitHandler' url: 'file:///e:/b/build/slave/vm-win32-release/build/dart/tools/testing/dart/test_runner.dart' line:584 col:19
 2. Function: '[email protected]' url: 'dart:io' line:6726 col:18
 3. Function: '[email protected]' url: 'dart:io' line:6732 col:53
 4. Function: '_SocketBase@14117cc4._multiplex@14117cc4' url: 'dart:io' line:7176 col:25
 5. Function: '[email protected]' url: 'dart:io' line:7289 col:59
 6. Function: '_ReceivePortImpl@6be832b._handleMessage@6be832b' url: 'dart:isolate' line:288 col:22

(code added in r4044)
-> error if (testCase.output.unexpectedOutput && testCase.configuration['verbose']) {

testCase.configuration['verbose'] must be initialized to false (it is null) or we must test :
     (testCase.configuration['verbose'] != null)