Add some basic interfaces that will be used for the test runner.

lib/src/test.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.test;
+
+import 'live_test.dart';
+import 'suite.dart';
+
+/// A single test.
+///
+/// A test is immutable and stateless, which means that it can't be run
+/// directly. To run one, load a live version using [Test.load] and run it using
+/// [LiveTest.run].
+abstract class Test {
+  /// The name of the test.
+  String get name;
+
+  /// Loads a live version of this test, which can be used to run it a single
+  /// time.
+  ///
+  /// [suite] is the suite within which this test is being run.
+  LiveTest load(Suite suite);
+}