Add writeAsStringSync (issue 27109)

pkg/analyzer/test/file_system/physical_resource_provider_test.dart

 // Copyright (c) 2014, 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.test.file_system.physical_resource_provider_test;
 
 import 'dart:async';
 import 'dart:core' hide Resource;
 import 'dart:io' as io;
 
@@ skipping 177 matching lines @@
     expect(file.toString(), path);
   }
 
   void test_toUri() {
     String path = '/foo/file.txt';
     File file = PhysicalResourceProvider.INSTANCE.getFile(path);
     expect(file.toUri(), new Uri.file(path));
   }
 
   void test_writeAsBytesSync() {
-    new io.File(path).writeAsBytesSync(<int>[1, 2]);
-    expect(file.readAsBytesSync(), <int>[1, 2]);
+    List<int> content = <int>[1, 2];
+    new io.File(path).writeAsBytesSync(content);
+    expect(file.readAsBytesSync(), content);
     // write new bytes
-    file.writeAsBytesSync(<int>[10, 20]);
-    expect(file.readAsBytesSync(), <int>[10, 20]);
+    content = <int>[10, 20];
+    file.writeAsBytesSync(content);
+    expect(file.readAsBytesSync(), content);
+  }
+
+  void test_writeAsStringSync() {
+    String content = 'ab';
+    new io.File(path).writeAsStringSync(content);
+    expect(file.readAsStringSync(), content);
+    // write new bytes
+    content = 'CD';
+    file.writeAsStringSync(content);
+    expect(file.readAsStringSync(), content);
   }
 }
 
 @reflectiveTest
 class FolderTest extends _BaseTest {
   String path;
   Folder folder;
 
   setUp() {
     super.setUp();
@@ skipping 359 matching lines @@
 
   setUp() {
     tempDirectory = io.Directory.systemTemp.createTempSync('test_resource');
     tempPath = tempDirectory.absolute.path;
   }
 
   tearDown() {
     tempDirectory.deleteSync(recursive: true);
   }
 }