Fix bug in BytesBuilder. Add tests.

tests/standalone/io/bytes_builder_test.dart

Index: tests/standalone/io/bytes_builder_test.dart
diff --git a/tests/standalone/io/bytes_builder_test.dart b/tests/standalone/io/bytes_builder_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..7dd49094d9676fe6fc446b56152ac9796eb82eaa
--- /dev/null
+++ b/tests/standalone/io/bytes_builder_test.dart
@@ -0,0 +1,64 @@
+// 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.
+
+import "dart:io";
+import "dart:typed_data";
+import "package:expect/expect.dart";
+
+main() {
+  for (var copying in [true, false]) {
+    var b;
+    testLength(n) {
+      Expect.equals(n, b.length);
+      if (n == 0) {
+        Expect.isTrue(b.isEmpty, "isEmpty: #${b.length}");
+        Expect.isFalse(b.isNotEmpty, "isNotEmpty: #${b.length}");
+      } else {
+        Expect.isTrue(b.isNotEmpty, "isNotEmpty: #${b.length}");
+        Expect.isFalse(b.isEmpty, "isEmpty: #${b.length}");
+      }
+    }
+
+    b = new BytesBuilder(copy: copying);
+    testLength(0);
+
+    b.addByte(0);
+    testLength(1);
+
+    b.add([1, 2, 3]);
+    testLength(4);
+
+    b.add(<int>[4, 5, 6]);
+    testLength(7);
+
+    b.add(new Uint8List.fromList([7, 8, 9]));
+    testLength(10);
+
+    b.add(new Uint16List.fromList([10, 11, 12]));
+    testLength(13);
+
+    var bytes = b.toBytes();
+    Expect.isTrue(bytes is Uint8List);
+    Expect.listEquals([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12], bytes);
+    testLength(13);
+
+    b.add("\x0d\x0e\x0f".codeUnits);
+    testLength(16);
+
+    bytes = b.takeBytes();
+    testLength(0);
+    Expect.isTrue(bytes is Uint8List);
+    Expect.listEquals([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15],
+                      bytes);
+
+    b.addByte(0);
+    testLength(1);
+
+    b.clear();
+    testLength(0);
+
+    b.addByte(0);
+    testLength(1);
+  }
+}