Add pretty-printing to unittest and more thoroughly print values.

pkg/unittest/lib/src/utils.dart

+// Copyright (c) 2013, 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 utils;
+
+/**
+ * Returns the name of the type of [x], or "Unknown" if the type name can't be
+ * determined.
+ */
+String typeName(x) {
+  // dart2js blows up on some objects (e.g. window.navigator).
+  // So we play safe here.
+  try {
+    if (x == null) return "null";
+    return x.runtimeType.toString();
+  } catch (e) {
+    return "Unknown";
+  }
+}
+
+/**
+ * Returns [source] with any control characters replaced by their escape
+ * sequences.
+ *
+ * This doesn't add quotes to the string, but it does escape single quote
+ * characters so that single quotes can be applied externally.
+ */
+String escapeString(String source) =>
+    source.split("").map(_escapeChar).join("");
+
+/** Return the escaped form of a character [ch]. */
+String _escapeChar(String ch) {
+  if (ch == "'")
+    return "\\'";
+  else if (ch == '\n')
+    return '\\n';
+  else if (ch == '\r')
+    return '\\r';
+  else if (ch == '\t')
+    return '\\t';
+  else
+    return ch;
+}
+