Make `analyzer_cli` tests bot-friendly (#25001).

pkg/analyzer_cli/test/strong_mode_test.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library analyzer_cli.test.strong_mode;
 
 import 'dart:io';
 
 import 'package:analyzer_cli/src/driver.dart' show Driver, errorSink, outSink;
 import 'package:path/path.dart' as path;
 import 'package:unittest/unittest.dart';
 
 import 'driver_test.dart';
 import 'utils.dart';
 
 /// End-to-end test for --strong checking.
 ///
 /// Most strong mode tests are in Analyzer, but this verifies the option is
 /// working and producing extra errors as expected.
 ///
 /// Generally we don't want a lot of cases here as it requires spinning up a
 /// full analysis context.
 ///
-// TODO(pq): fix tests to run safely on the bots
-// https://github.com/dart-lang/sdk/issues/25001
-main() {}
-not_main() {
+main() {
   group('--strong', () {
     StringSink savedOutSink, savedErrorSink;
     int savedExitCode;
     setUp(() {
       savedOutSink = outSink;
       savedErrorSink = errorSink;
       savedExitCode = exitCode;
       outSink = new StringBuffer();
       errorSink = new StringBuffer();
     });
     tearDown(() {
       outSink = savedOutSink;
       errorSink = savedErrorSink;
       exitCode = savedExitCode;
     });
 
     test('produces stricter errors', () async {
-      var testPath = path.join(testDirectory, 'data/strong_example.dart');
-      new Driver().start(['--options', emptyOptionsFile, '--strong', testPath]);
+      drive('data/strong_example.dart', args: ['--strong']);
 
       expect(exitCode, 3);
       var stdout = outSink.toString();
       expect(stdout, contains('[error] Invalid override'));
       expect(stdout, contains('[error] Type check failed'));
       expect(stdout, contains('2 errors found.'));
       expect(errorSink.toString(), '');
     });
   });
 }