First stab at a dev server in pub using barback.

sdk/lib/_internal/pub/test/serve/utils.dart

Index: sdk/lib/_internal/pub/test/serve/utils.dart
diff --git a/sdk/lib/_internal/pub/test/serve/utils.dart b/sdk/lib/_internal/pub/test/serve/utils.dart
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+++ b/sdk/lib/_internal/pub/test/serve/utils.dart
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+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS d.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 d.file.
+
+library pub_tests;
+
+import 'dart:async';
+import 'dart:io';
+
+import 'package:http/http.dart' as http;
+import 'package:scheduled_test/scheduled_process.dart';
+import 'package:scheduled_test/scheduled_test.dart';
+
+import '../descriptor.dart' as d;
+import '../test_pub.dart';
+
+/// The pub process running "pub serve".
+ScheduledProcess _pubServer;
+
+/// The ephemeral port assigned to the running server.
+int _port;
+
+/// Schedules starting the "pub serve" process.
+void startPubServe() {
+  // Use port 0 to get an ephemeral port.
+  _pubServer = startPub(args: ["serve", "--port=0"]);
+
+  schedule(() => _pubServer.nextLine().then((line) {

[nweiz, 2013/07/25 22:58:58]

[ScheduledProcess.nextLine] is automatically scheduled, so there's no need for
the extra [schedule] call here.

[Bob Nystrom, 2013/07/26 20:20:11]

Done.

+    var match = new RegExp(r"localhost:(\d+)\.").firstMatch(line);
+    assert(match != null);
+    _port = int.parse(match[1]);
+  }), "wait for pub server to start");
+}
+
+void endPubServe() {
+  _pubServer.kill();
+}
+
+/// Schedules an HTTP request to the running pub server with [urlPath] and
+/// verifies that it responds with [expected].
+void requestShouldSucceed(String urlPath, String expected) {
+  schedule(() {
+    return http.get("http://127.0.0.1:$_port/$urlPath").then((response) {
+      expect(response.body, equals(expected));
+    });
+  }, "request $urlPath");
+}
+
+/// Schedules an HTTP request to the running pub server with [urlPath] and
+/// verifies that it responds with a 404.
+void requestShould404(String urlPath) {
+  schedule(() {
+    return http.get("http://127.0.0.1:$_port/$urlPath").then((response) {
+      expect(response.statusCode, equals(404));
+    });
+  }, "request $urlPath");
+}