Throw a StateError if read()/readAsString() is called multiple times

dart/pkg/shelf/test/message_test.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.
 
 library shelf.message_test;
 
 import 'dart:async';
 import 'dart:convert';
 
 import 'package:shelf/src/message.dart';
@@ skipping 113 matching lines @@
         WORLD_BYTES
       ])));
 
       controller.add(HELLO_BYTES);
       return new Future(() {
         controller
           ..add(WORLD_BYTES)
           ..close();
       });
     });
+
+    test("throws when calling read()/readAsString() multiple times", () {
+      var request;
+
+      request = _createMessage();
+      expect(request.read().toList(), completion(isEmpty));
+      expect(() => request.read(), throwsStateError);
+
+      request = _createMessage();
+      expect(request.readAsString(), completion(isEmpty));
+      expect(() => request.readAsString(), throwsStateError);
+
+      request = _createMessage();
+      expect(request.readAsString(), completion(isEmpty));
+      expect(() => request.read(), throwsStateError);
+
+      request = _createMessage();
+      expect(request.read().toList(), completion(isEmpty));
+      expect(() => request.readAsString(), throwsStateError);
+    });
   });
 
   group("contentLength", () {
     test("is null without a content-length header", () {
       var request = _createMessage();
       expect(request.contentLength, isNull);
     });
 
     test("comes from the content-length header", () {
       var request = _createMessage(headers: {
@@ skipping 38 matching lines @@
       }).encoding, isNull);
     });
 
     test("comes from the content-type charset parameter", () {
       expect(_createMessage(headers: {
         'content-type': 'text/plain; charset=iso-8859-1'
       }).encoding, equals(LATIN1));
     });
   });
 }