Add Folder.getChildAssumingFile().

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 254 matching lines @@
     expect(child.exists, isTrue);
   }
 
   void test_getChild_folder() {
     provider.newFolder('/foo/bar/baz');
     Folder child = folder.getChild('baz');
     expect(child, isNotNull);
     expect(child.exists, isTrue);
   }
 
+  void test_getChildAssumingFile_doesNotExist() {
+    File child = folder.getChildAssumingFile('name');
+    expect(child, isNotNull);
+    expect(child.exists, isFalse);
+  }
+
+  void test_getChildAssumingFile_file() {
+    provider.newFile('/foo/bar/name', 'content');
+    File child = folder.getChildAssumingFile('name');
+    expect(child, isNotNull);
+    expect(child.exists, isTrue);
+  }
+
+  void test_getChildAssumingFile_folder() {
+    provider.newFolder('/foo/bar/name');
+    File child = folder.getChildAssumingFile('name');
+    expect(child, isNotNull);
+    expect(child.exists, isFalse);
+  }
+
   void test_getChildAssumingFolder_doesNotExist() {
     Folder child = folder.getChildAssumingFolder('foldername');
     expect(child, isNotNull);
     expect(child.exists, isFalse);
   }
 
   void test_getChildAssumingFolder_file() {
     provider.newFile('/foo/bar/foldername', 'content');
     Folder child = folder.getChildAssumingFolder('foldername');
     expect(child, isNotNull);
@@ skipping 354 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);
   }
 }