Add a Client class to json_rpc_2.

pkg/json_rpc_2/test/client/utils.dart

Index: pkg/json_rpc_2/test/client/utils.dart
diff --git a/pkg/json_rpc_2/test/client/utils.dart b/pkg/json_rpc_2/test/client/utils.dart
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+++ b/pkg/json_rpc_2/test/client/utils.dart
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+// 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 json_rpc_2.test.client.utils;
+
+import 'dart:async';
+import 'dart:convert';
+
+import 'package:json_rpc_2/json_rpc_2.dart' as json_rpc;
+import 'package:json_rpc_2/error_code.dart' as error_code;
+import 'package:unittest/unittest.dart';
+
+/// A controller used to test a [json_rpc.Client].
+class ClientController {
+  /// The controller for the client's response stream.
+  final _responseController = new StreamController<String>();
+
+  /// The controller for the client's request sink.
+  final _requestController = new StreamController<String>();
+
+  /// The client.
+  json_rpc.Client get client => _client;
+  json_rpc.Client _client;
+
+  ClientController() {
+    _client = new json_rpc.Client(
+        _responseController.stream, _requestController.sink);
+    _client.listen();
+  }
+
+  /// Expects that the client will send a request.
+  ///
+  /// The request is passed to [callback], which can return a response. If it
+  /// returns a String, that's sent as the response directly. If it returns
+  /// null, no response is sent. Otherwise, the return value is encoded and sent
+  /// as the response.
+  void expectRequest(callback(request)) {
+    expect(_requestController.stream.first.then((request) {
+      return callback(JSON.decode(request));
+    }).then((response) {
+      if (response == null) return;
+      if (response is! String) response = JSON.encode(response);
+      _responseController.add(response);
+    }), completes);
+  }
+
+  /// Sends [response], a decoded response, to [client].
+  Future sendResponse(response) => sendJsonResponse(JSON.encode(response));
+
+  /// Sends [response], a JSON-encoded response, to [client].
+  Future sendJsonResponse(String request) => _responseController.add(request);
+}
+
+/// Returns a [Future] that completes after pumping the event queue [times]
+/// times. By default, this should pump the event queue enough times to allow
+/// any code to run, as long as it's not waiting on some external event.
+Future pumpEventQueue([int times = 20]) {
+  if (times == 0) return new Future.value();
+  // We use a delayed future to allow microtask events to finish. The
+  // Future.value or Future() constructors use scheduleMicrotask themselves and
+  // would therefore not wait for microtask callbacks that are scheduled after
+  // invoking this method.
+  return new Future.delayed(Duration.ZERO, () => pumpEventQueue(times - 1));
+}