Adding to a closed sink throws.

tests/standalone/io/socket_exception_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.
 //
 // Tests socket exceptions.
 
 import "dart:async";
 import "dart:io";
 
 import "package:async_helper/async_helper.dart";
@@ skipping 72 matching lines @@
         Expect.isFalse(wrongExceptionCaught);
         try {
           client.destroy();
         } on SocketException catch (ex) {
           exceptionCaught = true;
         } catch (ex) {
           wrongExceptionCaught = true;
         }
         Expect.isFalse(exceptionCaught);
         Expect.isFalse(wrongExceptionCaught);
+
+        // From here exceptions are expected.
         try {
           List<int> buffer = new List<int>(10);
           client.add(buffer);
         } on StateError catch (ex) {
           exceptionCaught = true;
         } catch (ex) {
           wrongExceptionCaught = true;
         }
-        Expect.isFalse(exceptionCaught);
+        Expect.isTrue(exceptionCaught);
         Expect.isFalse(wrongExceptionCaught);
-
-        // From here exceptions are expected.
         exceptionCaught = false;
         try {
           client.port;
         } on SocketException catch (ex) {
           exceptionCaught = true;
         } catch (ex) {
           wrongExceptionCaught = true;
         }
         Expect.isTrue(exceptionCaught);
         Expect.isFalse(wrongExceptionCaught);
@@ skipping 155 matching lines @@
     clientSocketAddCloseResultErrorTest();
     unknownHostTest();
   }
 }
 
 main() {
   asyncStart();
   SocketExceptionTest.testMain();
   asyncEnd();
 }