Extend file-system abstraction with a couple methods, remove context

pkg/front_end/test/physical_file_system_test.dart

 // Copyright (c) 2016, 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.
 // SharedOptions=--supermixin
 
 library front_end.test.physical_file_system_test;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io' as io;
 
 import 'package:front_end/file_system.dart';
 import 'package:front_end/physical_file_system.dart';
 import 'package:path/path.dart' as p;
 import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(PhysicalFileSystemTest);
     defineReflectiveTests(FileTest);
+    defineReflectiveTests(DirectoryTest);
   });
 }
 
 @reflectiveTest
 class FileTest extends _BaseTest {
   String path;
   FileSystemEntity file;
 
   setUp() {
     super.setUp();
@@ skipping 47 matching lines @@
 
   test_readAsString_utf8() async {
     var bytes = [0xe2, 0x82, 0xac]; // Unicode € symbol (in UTF-8)
     new io.File(path).writeAsBytesSync(bytes);
     expect(await file.readAsString(), '\u20ac');
   }
 
   test_uri() {
     expect(file.uri, p.toUri(path));
   }
+
+  test_exists_doesNotExist() async {
+    expect(await file.exists(), isFalse);
+  }
+
+  test_exists_fileExists() async {
+    new io.File(path).writeAsStringSync('contents');
+    expect(await file.exists(), isTrue);
+  }
+
+  test_lastModified_increasesOnEachChange() async {
+    new io.File(path).writeAsStringSync('contents1');
+    var mod1 = await file.lastModified();
+
+    // Pause to ensure the file-system time-stamps are different.
+    await new Future.delayed(new Duration(seconds: 1));
+    new io.File(path).writeAsStringSync('contents2');
+    var mod2 = await file.lastModified();
+    expect(mod2.isAfter(mod1), isTrue);
+
+    await new Future.delayed(new Duration(seconds: 1));
+    var path2 = p.join(tempPath, 'file2.txt');
+    new io.File(path2).writeAsStringSync('contents2');
+    var file2 = entityForPath(path2);
+    var mod3 = await file2.lastModified();
+    expect(mod3.isAfter(mod2), isTrue);
+  }
 }
 
 @reflectiveTest
+class DirectoryTest extends _BaseTest {
+  String path;
+  FileSystemEntity dir;
+
+  setUp() {
+    super.setUp();
+    path = p.join(tempPath, 'dir');
+    dir = PhysicalFileSystem.instance.entityForUri(p.toUri(path));
+  }
+
+  test_equals_differentPaths() {
+    expect(dir == entityForPath(p.join(tempPath, 'dir2')), isFalse);
+  }
+
+  test_equals_samePath() {
+    expect(dir == entityForPath(p.join(tempPath, 'dir')), isTrue);
+  }
+
+  test_readAsBytes() async {
+    await new io.Directory(path).create();
+    expect(dir.readAsBytes(), throwsException);
+  }
+
+  test_uri() {
+    expect(dir.uri, p.toUri(path));
+  }
+
+  test_exists_doesNotExist() async {
+    expect(await dir.exists(), isFalse);
+  }
+
+  test_exists_directoryExists() async {
+    await new io.Directory(path).create();
+    expect(await dir.exists(), isTrue);
+  }
+}
+
+@reflectiveTest
 class PhysicalFileSystemTest extends _BaseTest {
   Uri tempUri;
 
   setUp() {
     super.setUp();
     tempUri = new Uri.directory(tempPath);
   }
 
   test_entityForPath() {
     var path = p.join(tempPath, 'file.txt');
@@ skipping 88 matching lines @@
       tempDirectory.deleteSync(recursive: true);
     } on io.FileSystemException {
       // Sometimes on Windows the delete fails with errno 32
       // (ERROR_SHARING_VIOLATION: The process cannot access the file because it
       // is being used by another process).  Wait 1 second and try again.
       await new Future.delayed(new Duration(seconds: 1));
       tempDirectory.deleteSync(recursive: true);
     }
   }
 }