Fix CLI SDK option config timing (#26129).

pkg/analyzer_cli/test/driver_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.driver;
 
 import 'dart:io';
 
 import 'package:analyzer/plugin/options.dart';
 import 'package:analyzer/source/analysis_options_provider.dart';
@@ skipping 245 matching lines @@
               outSink.toString(),
               contains(
                   "[error] This function declares a return type of 'int'"));
           expect(outSink.toString(), contains("1 error and 1 warning found."));
         });
 
         test('language', () {
           doDrive();
           expect(driver.context.analysisOptions.enableSuperMixins, isTrue);
         });
+
+        test('strongMode', () {
+          doDrive();
+          expect(driver.context.analysisOptions.strongMode, isTrue);
+          //https://github.com/dart-lang/sdk/issues/26129
+          AnalysisContext sdkContext =
+              driver.context.sourceFactory.dartSdk.context;
+          expect(sdkContext.analysisOptions.strongMode, isTrue);
+        });
       });
 
       group('with flags', () {
         // Shared driver command.
         var doDrive = () => drive('data/options_tests_project/test_file.dart',
             args: ['--fatal-warnings'],
             options: 'data/options_tests_project/.analysis_options');
 
         test('override fatal warning', () {
           doDrive();
@@ skipping 233 matching lines @@
     this.options = options;
   }
 }
 
 class TestSource implements Source {
   TestSource();
 
   @override
   noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
 }