Add a document-by-document JSON transformer.

test/json_document_transformer_test.dart

Index: test/json_document_transformer_test.dart
diff --git a/test/json_document_transformer_test.dart b/test/json_document_transformer_test.dart
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+++ b/test/json_document_transformer_test.dart
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+// Copyright (c) 2016, 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.
+
+import 'dart:async';
+import 'dart:convert';
+
+import 'package:stream_channel/stream_channel.dart';
+import 'package:test/test.dart';
+
+import 'utils.dart';
+
+void main() {
+  var streamController;
+  var sinkController;
+  var channel;
+  setUp(() {
+    streamController = new StreamController();
+    sinkController = new StreamController();
+    channel = new StreamChannel(
+        streamController.stream, sinkController.sink);
+  });
+
+  test("decodes JSON emitted by the channel", () {
+    var transformed = channel.transform(jsonDocument);
+    streamController.add('{"foo": "bar"}');
+    expect(transformed.stream.first, completion(equals({"foo": "bar"})));
+  });
+
+  test("encodes objects added to the channel", () {
+    var transformed = channel.transform(jsonDocument);
+    transformed.sink.add({"foo": "bar"});
+    expect(sinkController.stream.first,
+        completion(equals(JSON.encode({"foo": "bar"}))));
+  });
+
+  test("supports the reviver function", () {
+    var transformed = channel.transform(
+        new JsonDocumentTransformer(reviver: (key, value) => "decoded"));
+    streamController.add('{"foo": "bar"}');
+    expect(transformed.stream.first, completion(equals("decoded")));
+  });
+
+  test("supports the toEncodable function", () {
+    var transformed = channel.transform(
+        new JsonDocumentTransformer(toEncodable: (object) => "encoded"));
+    transformed.sink.add(new Object());
+    expect(sinkController.stream.first, completion(equals('"encoded"')));
+  });
+}