Add utility methods to write the contents of a file as one operation.

tests/standalone/io/file_write_as_test.dart

+// Copyright (c) 2012, 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.
+
+import 'dart:io';
+import 'dart:isolate';
+
+testWriteAsBytesSync(dir) {
+  var f = new File('${dir.path}/bytes_sync.txt');
+  var data = [50,50,50];
+  f.writeAsBytesSync(data);
+  Expect.listEquals(data, f.readAsBytesSync());
+  f.writeAsBytesSync(data, FileMode.APPEND);
+  var expected = [50, 50, 50, 50, 50, 50];
+  Expect.listEquals(expected, f.readAsBytesSync());
+}
+
+testWriteAsStringSync(dir) {
+  var f = new File('${dir.path}/string_sync.txt');
+  var data = 'asdf';
+  f.writeAsStringSync(data);
+  Expect.listEquals(data, f.readAsStringSync());
+  f.writeAsStringSync(data, FileMode.APPEND);
+  Expect.equals('$data$data', f.readAsStringSync());
+}
+
+Future testWriteAsBytes(dir) {
+  var completer = new Completer();
+  var f = new File('${dir.path}/bytes.txt');
+  var data = [50,50,50];
+  f.writeAsBytes(data).then((_){

[Søren Gjesse, 2012/11/20 13:23:34]

Maybe expect _ is f.

+    f.readAsBytes().then((bytes) {
+      Expect.listEquals(data, bytes);
+      f.writeAsBytes(data, FileMode.APPEND).then((_) {

[Søren Gjesse, 2012/11/20 13:23:34]

Ditto.

+        f.readAsBytes().then((bytes) {
+          var expected = [50, 50, 50, 50, 50, 50];
+          Expect.listEquals(expected, bytes);
+          completer.complete(true);
+        });
+      });
+    });
+  });
+  return completer.future;
+}
+
+Future testWriteAsString(dir) {
+  var completer = new Completer();
+  var f = new File('${dir.path}/strings.txt');
+  var data = 'asdf';
+  f.writeAsString(data).then((_){

[Søren Gjesse, 2012/11/20 13:23:34]

Ditto.

+    f.readAsString().then((str) {
+      Expect.equals(data, str);
+      f.writeAsString(data, FileMode.APPEND).then((_) {

[Søren Gjesse, 2012/11/20 13:23:34]

Ditto.

+        f.readAsString().then((str) {
+          Expect.equals('$data$data', str);
+          completer.complete(true);
+        });
+      });
+    });
+  });
+  return completer.future;
+}
+
+main() {
+  var port = new ReceivePort();
+  var tempDir = new Directory('').createTempSync();
+  testWriteAsBytesSync(tempDir);
+  testWriteAsStringSync(tempDir);
+  testWriteAsBytes(tempDir).chain((_) {
+    return testWriteAsString(tempDir);
+  }).then((_) {
+    tempDir.deleteSync(recursive: true);
+    port.close();
+  });
+}