Use Directory.systemTemp getter in pkg subdirectory of repository.

pkg/barback/test/asset_test.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.
 
 library barback.test.asset_test;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 
 import 'package:barback/barback.dart';
 import 'package:path/path.dart' as pathos;
 import 'package:unittest/unittest.dart';
 
 import 'utils.dart';
 
 /// The contents of the test binary file.
 final binaryContents = [0, 1, 2, 3, 4];
 
 main() {
   initConfig();
 
   Directory tempDir;
   String binaryFilePath;
   String textFilePath;
   String latin1FilePath;
 
   setUp(() {
     // Create a temp file we can use for assets.
-    tempDir = new Directory("").createTempSync();
+    tempDir = Directory.systemTemp.createTempSync('barback_asset_test_');
     binaryFilePath = pathos.join(tempDir.path, "file.bin");
     new File(binaryFilePath).writeAsBytesSync(binaryContents);
 
     textFilePath = pathos.join(tempDir.path, "file.txt");
     new File(textFilePath).writeAsStringSync("çøñ†éℵ™");
 
     latin1FilePath = pathos.join(tempDir.path, "file.latin1");
     new File(latin1FilePath).writeAsBytesSync(LATIN1.encode("blåbærgrød"));
   });
 
@@ skipping 168 matching lines @@
     });
 
     group("file asset", () {
       test("shows the file path", () {
         var asset = new Asset.fromPath(id, "path.txt");
         expect(asset.toString(), equals('File "path.txt"'));
       });
     });
   });
 }