fixes #168, dart:js implementation with a test

test/browser/minitest.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.
+
+// TODO(jmesserly): replace this with the real package:test.
+// Not possible yet because it uses on async/await which we don't support.
+library minitest;
+
+import 'dom.dart';
+
+final console = (window as dynamic).console;
+
+void group(String name, void body()) {
+  console.group(name);
+  body();
+  console.groupEnd(name);
+}
+
+void test(String name, void body(), {String skip}) {
+  if (skip != null) {
+    console.warn('SKIP $name: $skip');
+    return;
+  }
+  console.log(name);
+  try {
+    body();
+  } catch(e) {
+    console.error(e);
+  }
+}
+
+void expect(Object actual, matcher) {
+  if (matcher is! Matcher) matcher = equals(matcher);
+  if (!matcher(actual)) {
+    throw 'Expect failed to match $actual with $matcher';
+  }
+}
+
+Matcher equals(Object expected) {
+  return (actual) {
+    if (expected is List && actual is List) {
+      int len = expected.length;
+      if (len != actual.length) return false;
+      for (int i = 0; i < len; i++) {
+        if (!equals(expected[i])(actual[i])) return false;
+      }
+      return true;
+    } else {
+      return expected == actual;
+    }
+  };
+}
+
+Matcher same(Object expected) => (actual) => identical(expected, actual);
+Matcher isNot(matcher) {
+  if (matcher is! Matcher) matcher = equals(matcher);
+  return (actual) => !matcher(actual);
+}
+
+bool isNull(actual) => actual == null;
+final Matcher isNotNull = isNot(isNull);
+bool isRangeError(actual) => actual is RangeError;
+bool isNoSuchMethodError(actual) => actual is NoSuchMethodError;
+
+Matcher throwsA(matcher) {
+  if (matcher is! Matcher) matcher = equals(matcher);
+  return (actual) {
+    try {
+      actual();
+      return false;
+    } catch(e) {
+      return matcher(e);
+    }
+  };
+}
+
+final Matcher throws = throwsA((a) => true);
+
+typedef Matcher(actual);