diff --git a/swh/core/tests/test_config.py b/swh/core/tests/test_config.py
index dd08cfb..7b06ef1 100644
--- a/swh/core/tests/test_config.py
+++ b/swh/core/tests/test_config.py
@@ -1,87 +1,85 @@
 # Copyright (C) 2015  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 import tempfile
 import unittest
 import os
 import shutil
 
 from nose.tools import istest
 
 from swh.core import config
 
 
 def prepare_dummy_conf_file(tmp_dir):
     tmp_conf_file = tempfile.NamedTemporaryFile(
         mode='w', suffix="swh-core-test-read-conf",
-        dir=tmp_dir, delete=False)
+        delete=False)
     with open(tmp_conf_file.name, 'w') as f:
         f.write("""[main]
 a = 1
 b = this is a string
 c = true
 """)
     return tmp_conf_file.name
 
 
 class ConfReaderTest(unittest.TestCase):
 
     @classmethod
     def setUp(self):
         # create a temporary folder
-        self.tmp_work_folder = tempfile.mkdtemp(
-            prefix='test-swh-core.', dir='/tmp')
-
+        self.tmp_work_folder = tempfile.mkdtemp(prefix='test-swh-core.')
         self.tmp_conf_file = prepare_dummy_conf_file(self.tmp_work_folder)
 
     @classmethod
     def teardown(self):
         shutil.rmtree(self.tmp_work_folder)
 
     @istest
     def read(self):
         # given
         default_conf = {'a': ('int', 2),
                         'b': ('string', 'default-string'),
                         'c': ('bool', True),
                         'd': ('int', 10)}
 
         # when
         res = config.read(self.tmp_conf_file, default_conf)
 
         # then
         self.assertEquals(res, {'a': 1,
                                 'b': 'this is a string',
                                 'c': True,
                                 'd': 10})
 
     @istest
     def prepare_folder(self):
         # given
         conf = {'path1': self.tmp_work_folder + 'path1',
                 'path2': self.tmp_work_folder + 'path2/depth1'}
 
         # the folders does not exists
         self.assertFalse(os.path.exists(conf['path1']),
                          "path1 should not exist.")
         self.assertFalse(os.path.exists(conf['path2']),
                          "path2 should not exist.")
 
         # when
         config.prepare_folders(conf, 'path1')
 
         # path1 exists but not path2
         self.assertTrue(os.path.exists(conf['path1']),
                         "path1 should now exist!")
         self.assertFalse(os.path.exists(conf['path2']),
                          "path2 should not exist.")
 
         # path1 already exists, skips it but creates path2
         config.prepare_folders(conf, 'path1', 'path2')
 
         self.assertTrue(os.path.exists(conf['path1']),
                         "path1 should still exist!")
         self.assertTrue(os.path.exists(conf['path2']),
                         "path2 should now exist.")