anchor.diff:  }
   
   abstract class _MigrationCliTestBase {
  +  Map<String, String> environmentVariables = {};
  +
  +  /// If `true`, then an artificial exception should be generated when migration
  +  /// encounters a reference to the `print` function.
  +  bool injectArtificialException = false;
  +
     void set logger(_TestLogger logger);
   
     _MockProcessManager get processManager;
  
positive.code:   test_lifecycle_exception_handling_ignore() async {
      var projectContents = simpleProject(sourceText: 'main() { print(0); }');
      var projectDir = await createProjectDir(projectContents);
      var cli = _createCli(injectArtificialException: true);
      await runWithPreviewServer(cli, ['--ignore-exceptions', projectDir],
          (url) async {
        var output = logger.stdoutBuffer.toString();
  
negative.code:       {List<String> included = const <String>[],
        int preferredPort,
        String summaryPath}) {
      if (cli._test.injectArtificialException) {
        return _ExceptionGeneratingNonNullableFix(
            listener, resourceProvider, getLineInfo,
            included: included,
  