Add a ConsoleReporter for printing human-friendly test progress reports.

lib/src/io.dart

+// Copyright (c) 2015, 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 unittest.io;
+
+import 'dart:io';
+
+/// Whether "special" strings such as Unicode characters or color escapes are
+/// safe to use.
+///
+/// On Windows or when not printing to a terminal, only printable ASCII
+/// characters should be used.
+bool get canUseSpecialChars =>
+    Platform.operatingSystem != 'windows' &&
+    stdioType(stdout) == StdioType.TERMINAL;
+
+/// Gets a "special" string (ANSI escape or Unicode).
+///
+/// On Windows or when not printing to a terminal, returns something else since
+/// those aren't supported.
+String getSpecial(String special, [String onWindows = '']) =>
+    canUseSpecialChars ? special : onWindows;