Replace the existing unittest APIs with the new runner infrastructure.

lib/src/group_context.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.group_context;
-
-import 'dart:async';
-
-import '../unittest.dart';
-
-/// Setup and teardown functions for a group and its parents, the latter
-/// for chaining.
-class GroupContext {
-  /// The parent context, or `null`.
-  final GroupContext parent;
-
-  /// Whether this is the root context.
-  bool get isRoot => parent == null;
-
-  /// Description text of the current test group.
-  final String _name;
-
-  /// The set-up function called before each test in a group.
-  Function get testSetUp => _testSetUp;
-  Function _testSetUp;
-
-  set testSetUp(Function setUp) {
-    if (parent == null || parent.testSetUp == null) {
-      _testSetUp = setUp;
-      return;
-    }
-
-    _testSetUp = () {
-      var f = parent.testSetUp();
-      if (f is Future) {
-        return f.then((_) => setUp());
-      } else {
-        return setUp();
-      }
-    };
-  }
-
-  /// The tear-down function called after each test in a group.
-  Function get testTearDown => _testTearDown;
-  Function _testTearDown;
-
-  set testTearDown(Function tearDown) {
-    if (parent == null || parent.testTearDown == null) {
-      _testTearDown = tearDown;
-      return;
-    }
-
-    _testTearDown = () {
-      var f = tearDown();
-      if (f is Future) {
-        return f.then((_) => parent.testTearDown());
-      } else {
-        return parent.testTearDown();
-      }
-    };
-  }
-
-  /// Returns the fully-qualified name of this context.
-  String get fullName =>
-      (isRoot || parent.isRoot) ? _name : "${parent.fullName}$groupSep$_name";
-
-  GroupContext.root()
-      : parent = null,
-        _name = '';
-
-  GroupContext(this.parent, this._name) {
-    _testSetUp = parent.testSetUp;
-    _testTearDown = parent.testTearDown;
-  }
-}