Enhance the Dart unittest library to support multiple invocations in the same application run.

pkg/unittest/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.
+
+part of unittest;
+
+/// Class for encapsulating test environment state.
+///
+/// This is used by the [withTestEnvironment] method to support multiple
+/// invocations of the unittest library within the same application
+/// instance.
+class _TestEnvironment {
+  Configuration config;
+
+  // 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();
+  _GroupContext currentContext;
+
+  /// The [currentTestCaseIndex] represents the index of the currently running
+  /// test case.
+  ///
+  /// == -1 implies the test system is not running.
+  /// == [number of test cases] is a short-lived state flagging that the last
+  ///    test has completed.

[nweiz, 2014/11/17 23:02:55]

Don't start sentences with "=="; use something like "If this is -1, that means
the test system isn't running."

[wibling, 2014/11/18 10:16:49]

Sure. I have fixed it.

+  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 set of tests to run can be restricted by using [solo_test] and
+  /// [solo_group].
+  ///
+  /// As groups can be nested we use a counter to keep track of the nesting
+  /// level of soloing, and a flag to tell if we have seen any solo tests.
+  int soloNestingLevel = 0;
+  bool soloTestSeen = false;
+
+  /// The list of test cases to run.
+  final List<TestCase> testCases = new List<TestCase>();

[nweiz, 2014/11/17 23:02:55]

There's no need to type annotate this, since the type is clear from the
initializing expression.

[wibling, 2014/11/18 10:16:49]

I am getting mixed feedback here. As far as I have heard and also my personal
preference we should type annotate fields that are public. Even in a private
class.

[nweiz, 2014/11/19 21:40:39]

The code in the repo isn't entirely consistent, but across most of the
widely-used Dart-team-authored packages the convention is to include types on
*most* instance variables but to omit them when there's an initializer that
makes the type clear. Basically, the minimum amount of verbosity should be used
that still makes the type clear from the declaration.

+
+  /// The [uncaughtErrorMessage] holds the error messages that are printed
+  /// in the test summary.
+  String uncaughtErrorMessage;
+
+  _TestEnvironment() {
+    currentContext = rootContext;
+  }
+}