Replace the existing unittest APIs with the new runner infrastructure.

lib/src/test_environment.dart

-// Copyright (c) 2014, 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.test_environment;
-
-import 'dart:async';
-
-import 'configuration.dart';
-import 'group_context.dart';
-import 'internal_test_case.dart';
-
-/// The default unittest environment.
-final _defaultEnvironment = new TestEnvironment();
-
-/// The current unittest environment.
-TestEnvironment get environment {
-  var environment = Zone.current[#unittest.environment];
-  return environment == null ? _defaultEnvironment : environment;
-}
-
-// The current environment's configuration.
-Configuration get config => environment.config;
-
-/// Encapsulates the state of the test environment.
-///
-/// This is used by the [withTestEnvironment] method to support multiple
-/// invocations of the unittest library within the same application
-/// instance.
-class TestEnvironment {
-  /// The environment's configuration.
-  Configuration config;
-
-  /// The top-level group context.
-  ///
-  /// We use a 'dummy' context for the top level to eliminate null checks when
-  /// querying the context. This allows us to easily support top-level
-  /// [setUp]/[tearDown] functions as well.
-  final rootContext = new GroupContext.root();
-
-  /// The current group context.
-  GroupContext currentContext;
-
-  /// The [currentTestCaseIndex] represents the index of the currently running
-  /// test case.
-  ///
-  /// If this is -1 it implies the test system is not running.
-  /// It will be set to [number of test cases] as a short-lived state flagging
-  /// that the last test has completed.
-  int currentTestCaseIndex = -1;
-
-  /// The [initialized] variable specifies whether the framework
-  /// has been initialized.
-  bool initialized = false;
-
-  /// The time since we last gave asynchronous code a chance to be scheduled.
-  int lastBreath = new DateTime.now().millisecondsSinceEpoch;
-
-  /// The number of [solo_group]s deep we are currently.
-  int soloNestingLevel = 0;
-
-  /// Whether we've seen a [solo_test].
-  bool soloTestSeen = false;
-
-  /// The list of test cases to run.
-  final testCases = new List<InternalTestCase>();
-
-  /// The error message that is printed in the test summary.
-  String uncaughtErrorMessage;
-
-  TestEnvironment() {
-    currentContext = rootContext;
-  }
-}