Use the polling watcher by default in pub tests for now.

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

 // Copyright (c) 2013, 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 file.
 
 library pub_tests;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 
@@ skipping 74 matching lines @@
       transform.addOutput(new Asset.fromString(transform.primaryInput.id,
           contents.replaceAllMapped(_tokenRegExp, (match) {
         return 'const TOKEN = "(\${match[1]}, \$TOKEN)";';
       })));
     });
   }
 }
 """;
 }
 
-/// Schedules starting the "pub serve" process.
+/// Schedules starting the `pub serve` process.
 ///
-/// If [shouldGetFirst] is `true`, validates that pub get is run first. If
-/// [dart2js] is `false`, does not compile Dart entrypoints in "web" to
-/// JavaScript.
+/// Unlike [pubServe], this doesn't determine the port number of the server, and
+/// so may be used to test for errors in the initialization process.
 ///
 /// Returns the `pub serve` process.
-ScheduledProcess startPubServe({bool shouldGetFirst: false,
-    Iterable<String> args}) {
+ScheduledProcess startPubServe([Iterable<String> args]) {
   // Use port 0 to get an ephemeral port.
-  var pubArgs = ["serve", "--port=0", "--hostname=127.0.0.1"];
+  var pubArgs = ["serve", "--port=0", "--hostname=127.0.0.1", "--force-poll"];
 
   if (args != null) pubArgs.addAll(args);
 
   // Dart2js can take a long time to compile dart code, so we increase the
   // timeout to cope with that.
   currentSchedule.timeout = new Duration(seconds: 15);
 
-  _pubServer = startPub(args: pubArgs);
+  return startPub(args: pubArgs);
+}
+
+/// Schedules starting the "pub serve" process and records its port number for
+/// future requests.
+///
+/// If [shouldGetFirst] is `true`, validates that pub get is run first.
+///
+/// Returns the `pub serve` process.
+ScheduledProcess pubServe({bool shouldGetFirst: false,
+    Iterable<String> args}) {
+  _pubServer = startPubServe(args);
 
   currentSchedule.onComplete.schedule(() {
     if (_webSocket != null) {
       _webSocket.close();
       _webSocket = null;
       _webSocketBroadcastStream = null;
     }
   });
 
   if (shouldGetFirst) {
@@ skipping 98 matching lines @@
 /// socket. It omitted, request is JSON encoded to a string first.
 void webSocketShouldReply(request, expectation, {bool encodeRequest: true}) {
   schedule(() => _ensureWebSocket().then((_) {
     if (encodeRequest) request = JSON.encode(request);
     _webSocket.add(request);
     return _webSocketBroadcastStream.first.then((value) {
       expect(JSON.decode(value), expectation);
     });
   }), "send $request to web socket and expect reply that $expectation");
 }