Add test- and group-level support for skipping tests.

lib/test.dart

 // Copyright (c) 2013, 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 test;
 
 import 'dart:async';
 
 import 'package:path/path.dart' as p;
 
@@ skipping 54 matching lines @@
 ///
 /// The description will be added to the descriptions of any surrounding
 /// [group]s. If [testOn] is passed, it's parsed as a [platform selector][]; the
 /// test will only be run on matching platforms.
 ///
 /// [platform selector]: https://github.com/dart-lang/test/#platform-selector-syntax
 ///
 /// If [timeout] is passed, it's used to modify or replace the default timeout
 /// of 30 seconds. Timeout modifications take precedence in suite-group-test
 /// order, so [timeout] will also modify any timeouts set on the group or suite.
-void test(String description, body(), {String testOn, Timeout timeout}) =>
-    _declarer.test(description, body, testOn: testOn, timeout: timeout);
+///
+/// If [skip] is a String or `true`, the test is skipped. If it's a String, it
+/// should explain why the test is skipped; this reason will be printed instead
+/// of running the test.
+void test(String description, body(), {String testOn, Timeout timeout,
+        skip}) =>
+    _declarer.test(description, body,
+        testOn: testOn, timeout: timeout, skip: skip);
 
 /// Creates a group of tests.
 ///
 /// A group's description is included in the descriptions of any tests or
 /// sub-groups it contains. [setUp] and [tearDown] are also scoped to the
 /// containing group.
 ///
 /// If [testOn] is passed, it's parsed as a [platform selector][]; the test will
 /// only be run on matching platforms.
 ///
 /// [platform selector]: https://github.com/dart-lang/test/#platform-selector-syntax
 ///
 /// If [timeout] is passed, it's used to modify or replace the default timeout
 /// of 30 seconds. Timeout modifications take precedence in suite-group-test
 /// order, so [timeout] will also modify any timeouts set on the suite, and will
 /// be modified by any timeouts set on individual tests.
-void group(String description, void body(), {String testOn, Timeout timeout}) =>
-    _declarer.group(description, body, testOn: testOn, timeout: timeout);
+///
+/// If [skip] is a String or `true`, the group is skipped. If it's a String, it
+/// should explain why the group is skipped; this reason will be printed instead
+/// of running the group's tests.
+void group(String description, void body(), {String testOn, Timeout timeout,
+        skip}) =>
+    _declarer.group(description, body,
+        testOn: testOn, timeout: timeout, skip: skip);
 
 /// Registers a function to be run before tests.
 ///
 /// This function will be called before each test is run. [callback] may be
 /// asynchronous; if so, it must return a [Future].
 ///
 /// If this is called within a test group, it applies only to tests in that
 /// group. [callback] will be run after any set-up callbacks in parent groups or
 /// at the top level.
 void setUp(callback()) => _declarer.setUp(callback);
@@ skipping 10 matching lines @@
 
 /// Handle an error that occurs outside of any test.
 void handleExternalError(error, String message, [stackTrace]) {
   // TODO(nweiz): handle this better.
   registerException(error, stackTrace);
 }
 
 /// Registers an exception that was caught for the current test.
 void registerException(error, [StackTrace stackTrace]) =>
     Invoker.current.handleError(error, stackTrace);