e2e test for transformer (webdriver + pub serve)

test/child_server_process.dart

+// 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:io';
+import 'dart:async';
+
+class ChildServerProcess {
+  /// [IOSink]s like [stdout] don't like to be piped more than one [Stream], but
+  /// we want to pipe many of them (basically, every standard output and error
+  /// of every child process we open), so we pipe to an accommodating consumer.
+  static final _consoleOut = new _MultipleStreamConsumer(stdout);
+
+  final Process process;
+  final String host;
+  final int port;
+  ChildServerProcess._(this.process, this.host, this.port);
+
+  get httpUri => Uri.parse('http://$host:$port');
+
+  static build(Future<Process> builder(String host, int port),
+      {int defaultPort: 1024,
+      int maxPort: 65535,
+      String host: '0.0.0.0'}) async {
+    var port = await _findUnusedPort(defaultPort, maxPort);
+    var p = (await builder(host, port))
+      ..stdout.pipe(_consoleOut)
+      ..stderr.pipe(_consoleOut);
+    await _waitForServer(host, port);
+    return new ChildServerProcess._(p, host, port);
+  }
+
+  static _waitForServer(String host, int port,
+      {int attempts: 10,
+      Duration retryDelay: const Duration(seconds: 1)}) async {
+    var lastError;
+    for (int i = 0; i < attempts; i++) {
+      try {
+        await (await Socket.connect(host, port)).close();
+        return;
+      } catch (e) {
+        lastError = e;
+        await new Future.delayed(retryDelay);
+      }
+    }
+    throw new StateError(
+        'Failed to connect to $host:$port after $attempts attempts; '
+        'Last error:\n$lastError');
+  }
+
+  static Future<int> _findUnusedPort(int fromPort, int toPort) async {
+    var lastError;
+    for (int port = fromPort; port <= toPort; port++) {
+      try {
+        await (await ServerSocket.bind(InternetAddress.ANY_IP_V4, port))
+            .close();
+        return port;
+      } catch (e) {
+        lastError = e;
+      }
+    }
+    throw new StateError(
+        'Failed to find an unused port between $fromPort and $toPort; '
+        'Last error:\n$lastError');
+  }
+}
+
+/// A consumer into which we can pipe as many streams as we want, that forwards
+/// everything to an [IOSink] (such as [stdout]).
+class _MultipleStreamConsumer extends StreamConsumer<List<int>> {
+  final IOSink _sink;
+  _MultipleStreamConsumer(this._sink);
+
+  @override
+  Future addStream(Stream<List<int>> stream) async {
+    await for (var data in stream) {
+      _sink.add(data);
+    }
+  }
+
+  @override
+  close() {}
+}