Support running tests without a packages/ directory.

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.
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 import 'dart:math';
 
 import 'package:async/async.dart';
 import 'package:http/testing.dart';
+import 'package:package_resolver/package_resolver.dart';
 import 'package:path/path.dart' as p;
 import 'package:pub/src/entrypoint.dart';
 import 'package:pub/src/exceptions.dart';
 import 'package:pub/src/exit_codes.dart' as exit_codes;
 // TODO(rnystrom): Using "gitlib" as the prefix here is ugly, but "git" collides
 // with the git descriptor method. Maybe we should try to clean up the top level
 // scope a bit?
 import 'package:pub/src/git.dart' as gitlib;
 import 'package:pub/src/http.dart';
 import 'package:pub/src/io.dart';
@@ skipping 312 matching lines @@
 
   // If there's a snapshot available, use it. The user is responsible for
   // ensuring this is up-to-date..
   //
   // TODO(nweiz): When the test runner supports plugins, create one to
   // auto-generate the snapshot before each run.
   var pubPath = p.absolute(p.join(pubRoot, 'bin/pub.dart'));
   if (fileExists('$pubPath.snapshot')) pubPath += '.snapshot';
 
   var dartArgs = <dynamic>[
-    '--package-root=${p.toUri(p.absolute(p.fromUri(Platform.packageRoot)))}',
+    PackageResolver.current.processArgument,
     pubPath,
     '--verbose'
   ]..addAll(args);
 
   if (tokenEndpoint == null) tokenEndpoint = new Future.value();
   var environmentFuture = tokenEndpoint
       .then((tokenEndpoint) => getPubTestEnvironment(tokenEndpoint))
       .then((pubEnvironment) {
     if (environment != null) pubEnvironment.addAll(environment);
     return pubEnvironment;
@@ skipping 396 matching lines @@
         _lastMatcher.matches(item.last, matchState);
   }
 
   Description describe(Description description) {
     return description.addAll("(", ", ", ")", [_firstMatcher, _lastMatcher]);
   }
 }
 
 /// A [StreamMatcher] that matches multiple lines of output.
 StreamMatcher emitsLines(String output) => inOrder(output.split("\n"));