Add writeAsStringSync (issue 27109)

pkg/analyzer/test/file_system/memory_file_system_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.memory_file_system_test;
 
 import 'dart:async';
 import 'dart:core' hide Resource;
 
 import 'package:analyzer/file_system/file_system.dart';
@@ skipping 193 matching lines @@
     expect(file.toString(), '/foo/bar/file.txt');
   }
 
   void test_toUri() {
     String path = '/foo/file.txt';
     File file = provider.newFile(path, '');
     expect(file.toUri(), new Uri.file(path, windows: false));
   }
 
   void test_writeAsBytesSync_existing() {
-    File file = provider.newFileWithBytes('/foo/file.bin', <int>[1, 2]);
-    expect(file.readAsBytesSync(), <int>[1, 2]);
+    List<int> content = <int>[1, 2];
+    File file = provider.newFileWithBytes('/foo/file.bin', 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_writeAsBytesSync_new() {
     File file = provider.getFile('/foo/file.bin');
     expect(file.exists, false);
     // write new bytes
-    file.writeAsBytesSync(<int>[10, 20]);
+    List<int> content = <int>[10, 20];
+    file.writeAsBytesSync(content);
     expect(file.exists, true);
-    expect(file.readAsBytesSync(), <int>[10, 20]);
+    expect(file.readAsBytesSync(), content);
+  }
+
+  void test_writeAsStringSync_existing() {
+    String content = 'ab';
+    File file = provider.newFile('/foo/file.txt', content);
+    expect(file.readAsStringSync(), content);
+    // write new bytes
+    content = 'CD';
+    file.writeAsStringSync(content);
+    expect(file.readAsStringSync(), content);
+  }
+
+  void test_writeAsStringSync_new() {
+    File file = provider.getFile('/foo/file.txt');
+    expect(file.exists, false);
+    // write new bytes
+    String content = 'ef';
+    file.writeAsStringSync(content);
+    expect(file.exists, true);
+    expect(file.readAsStringSync(), content);
   }
 }
 
 @reflectiveTest
 class FolderTest {
   static const String path = '/foo/bar';
 
   MemoryResourceProvider provider = new MemoryResourceProvider();
   Folder folder;
 
@@ skipping 465 matching lines @@
     return new Future.delayed(Duration.ZERO, computation);
   }
 
   _watchingFolder(String path, test(List<WatchEvent> changesReceived)) {
     Folder folder = provider.getResource(path);
     var changesReceived = <WatchEvent>[];
     folder.changes.listen(changesReceived.add);
     return test(changesReceived);
   }
 }