Make expect* throw useful errors outside tests.

lib/src/frontend/expect_async.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 test.frontend.expect_async;
 
 import 'dart:async';
 
 import '../backend/invoker.dart';
 import '../backend/state.dart';
@@ skipping 202 matching lines @@
 ///
 /// [max] can be used to specify an upper bound on the number of calls; if this
 /// is exceeded the test will fail. If [max] is `0` (the default), the callback
 /// is expected to be called exactly [count] times. If [max] is `-1`, the
 /// callback is allowed to be called any number of times greater than [count].
 ///
 /// Both [id] and [reason] are optional and provide extra information about the
 /// callback when debugging. [id] should be the name of the callback, while
 /// [reason] should be the reason the callback is expected to be called.
 Function expectAsync(Function callback,
-        {int count: 1, int max: 0, String id, String reason}) =>
-    new _ExpectedFunction(callback, count, max, id: id, reason: reason).func;
+        {int count: 1, int max: 0, String id, String reason}) {
+  if (Invoker.current == null) {
+    throw new StateError("expectAsync() may only be called within a test.");
+  }
+
+  return new _ExpectedFunction(callback, count, max, id: id, reason: reason)
+      .func;
+}
 
 /// Indicate that [callback] is expected to be called until [isDone] returns
 /// true.
 ///
 /// [isDone] is called after each time the function is run. Only when it returns
 /// true will the callback be considered complete. [callback] may take up to six
 /// optional or required positional arguments; named arguments are not
 /// supported.
 ///
 /// Both [id] and [reason] are optional and provide extra information about the
 /// callback when debugging. [id] should be the name of the callback, while
 /// [reason] should be the reason the callback is expected to be called.
 Function expectAsyncUntil(Function callback, bool isDone(),
-    {String id, String reason}) => new _ExpectedFunction(callback, 0, -1,
-        id: id, reason: reason, isDone: isDone).func;
+    {String id, String reason}) {
+  if (Invoker.current == null) {
+    throw new StateError(
+        "expectAsyncUntil() may only be called within a test.");
+  }
+
+  return new _ExpectedFunction(callback, 0, -1,
+      id: id, reason: reason, isDone: isDone).func;
+}