Pub integration tests sometimes need more than 20 seconds.

dart/sdk/lib/_internal/pub/test/test_pub.dart

 // Copyright (c) 2013, 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.
 
 /// Test infrastructure for testing pub. Unlike typical unit tests, most pub
 /// tests are integration tests that stage some stuff on the file system, run
 /// pub, and then validate the results. This library provides an API to build
 /// tests like that.
 library test_pub;
 
@@ skipping 21 matching lines @@
 import '../lib/src/system_cache.dart';
 import '../lib/src/utils.dart';
 import '../lib/src/validator.dart';
 import 'descriptor.dart' as d;
 
 /// This should be called at the top of a test file to set up an appropriate
 /// test configuration for the machine running the tests.
 initConfig() {
   useCompactVMConfiguration();
   filterStacks = true;
+  unittestConfiguration.timeout = null;
 }
 
 /// Returns whether we're running on a Dart build bot.
 bool get runningOnBuildbot =>
   Platform.environment.containsKey('BUILDBOT_BUILDERNAME');
 
 /// The current [HttpServer] created using [serve].
 var _server;
 
 /// The list of paths that have been requested from the server since the last
@@ skipping 733 matching lines @@
   bool matches(item, Map matchState) {
     if (item is! Pair) return false;
     return _firstMatcher.matches(item.first, matchState) &&
         _lastMatcher.matches(item.last, matchState);
   }
 
   Description describe(Description description) {
     description.addAll("(", ", ", ")", [_firstMatcher, _lastMatcher]);
   }
 }