Support some file operations in dart:io under mojo

services/dart/dart_apptests/lib/src/file_apptests.dart

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+library file_apptests;
+
+import 'dart:async';
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:mojo_apptest/apptest.dart';
+import 'package:mojo/application.dart';
+import 'package:mojo/bindings.dart';
+import 'package:mojo/core.dart';
+
+tests(Application application, String url) {
+  group('File Apptests', () {
+    test('Absolute path', () async {
+      String current = Directory.current.path;
+      for (String relative in ['abd', '..', '.', 'efg/hij', 'abc/']) {
+        if (current.endsWith('/')) {
+          expect(new File(relative).absolute.path, '$current$relative');

[zra, 2015/12/18 22:51:46]

Is this shorthand for expect(x, equals(y))?

[Cutch, 2015/12/18 23:05:20]

yes

+        } else {
+          expect(new File(relative).absolute.path, '$current/$relative');
+        }
+        expect(new File(relative).absolute.isAbsolute, isTrue);
+        expect(new Directory(relative).absolute.path,
+               new Link(relative).absolute.path);
+        expect(new File(relative).absolute is File, isTrue);
+        expect(new Directory(relative).absolute is Directory, isTrue);
+        expect(new Link(relative).absolute is Link, isTrue);
+      }
+      for (String absolute in ['/abd', '/', '/./..\\', '/efg/hij', '/abc/']) {
+        expect(new File(absolute).absolute.path, absolute);
+        expect(new File(absolute).absolute.isAbsolute, isTrue);
+       }
+    });
+    test('File Constructor', () async {
+      expect(new File('blåbærgrød'), isNotNull);
+      expect(new File('foo.txt'), isNotNull);
+    });
+    test('Directory systemTemp', () async {
+      expect(Directory.systemTemp, isNotNull);
+    });
+    test('Directory create', () async {
+      Directory directory =
+          await Directory.systemTemp.createTemp('dart_directory_test');
+      Directory subDirectory = new Directory("${directory.path}/subdir");
+      expect('$directory'.contains(directory.path), isTrue);
+      expect(await subDirectory.exists(), isFalse);
+      await subDirectory.create();
+      expect(await subDirectory.exists(), isTrue);
+      File f = new File('${subDirectory.path}/file.txt');
+      File fLong = new File('${directory.path}/subdir/../subdir/file.txt');
+      expect(await f.exists(), isFalse);
+      await fLong.create();
+      expect(await f.exists(), isTrue);
+    });
+  });
+}