diff --git a/swh/lister/gnu/tests/tree.json b/swh/lister/gnu/tests/data/tree.json
similarity index 100%
rename from swh/lister/gnu/tests/tree.json
rename to swh/lister/gnu/tests/data/tree.json
diff --git a/swh/lister/gnu/tests/tree.min.json b/swh/lister/gnu/tests/data/tree.min.json
similarity index 100%
rename from swh/lister/gnu/tests/tree.min.json
rename to swh/lister/gnu/tests/data/tree.min.json
diff --git a/swh/lister/gnu/tests/test_tree.py b/swh/lister/gnu/tests/test_tree.py
index 3f0c5fe..5df141b 100644
--- a/swh/lister/gnu/tests/test_tree.py
+++ b/swh/lister/gnu/tests/test_tree.py
@@ -1,135 +1,135 @@
 # Copyright (C) 2019 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 json
 
 import pytest
 
 from os import path
 from swh.lister.gnu.tree import (
     GNUTree, find_artifacts, check_filename_is_archive, load_raw_data
 )
 
 
 def test_load_raw_data_from_query(requests_mock_datadir):
     actual_json = load_raw_data('https://ftp.gnu.org/tree.json.gz')
     assert actual_json is not None
     assert isinstance(actual_json, list)
     assert len(actual_json) == 2
 
 
 def test_load_raw_data_from_query_failure(requests_mock_datadir):
     inexistant_url = 'https://ftp2.gnu.org/tree.unknown.gz'
     with pytest.raises(ValueError, match='Error during query'):
         load_raw_data(inexistant_url)
 
 
 def test_load_raw_data_from_file(datadir):
     filepath = path.join(datadir, 'ftp.gnu.org', 'tree.json.gz')
     actual_json = load_raw_data(filepath)
     assert actual_json is not None
     assert isinstance(actual_json, list)
     assert len(actual_json) == 2
 
 
 def test_load_raw_data_from_file_failure(datadir):
     unknown_path = path.join(datadir, 'ftp.gnu.org2', 'tree.json.gz')
     with pytest.raises(FileNotFoundError):
         load_raw_data(unknown_path)
 
 
 def test_tree_json(requests_mock_datadir):
     tree_json = GNUTree('https://ftp.gnu.org/tree.json.gz')
 
     assert tree_json.projects['https://ftp.gnu.org/gnu/8sync/'] == {
         'name': '8sync',
         'time_modified': '1489817408',
         'url': 'https://ftp.gnu.org/gnu/8sync/'
     }
 
     assert tree_json.projects['https://ftp.gnu.org/gnu/3dldf/'] == {
         'name': '3dldf',
         'time_modified': '1386961236',
         'url': 'https://ftp.gnu.org/gnu/3dldf/'
     }
 
     assert tree_json.projects['https://ftp.gnu.org/gnu/a2ps/'] == {
         'name': 'a2ps',
         'time_modified': '1198900505',
         'url': 'https://ftp.gnu.org/gnu/a2ps/'
     }
 
     assert tree_json.projects['https://ftp.gnu.org/old-gnu/xshogi/'] == {
         'name': 'xshogi',
         'time_modified': '1059822922',
         'url': 'https://ftp.gnu.org/old-gnu/xshogi/'
     }
 
     assert tree_json.artifacts['https://ftp.gnu.org/old-gnu/zlibc/'] == [
         {
             'archive': 'https://ftp.gnu.org/old-gnu/zlibc/zlibc-0.9b.tar.gz',  # noqa
             'length': 90106,
             'time': 857980800
         },
         {
             'archive': 'https://ftp.gnu.org/old-gnu/zlibc/zlibc-0.9e.tar.gz',  # noqa
             'length': 89625,
             'time': 860396400
         }
     ]
 
 
 def test_tree_json_failures(requests_mock_datadir):
     url = 'https://unknown/tree.json.gz'
     tree_json = GNUTree(url)
 
     with pytest.raises(ValueError, match='Error during query to %s' % url):
         tree_json.artifacts['https://ftp.gnu.org/gnu/3dldf/']
 
     with pytest.raises(ValueError, match='Error during query to %s' % url):
         tree_json.projects['https://ftp.gnu.org/old-gnu/xshogi/']
 
 
-def test_find_artifacts_small_sample():
+def test_find_artifacts_small_sample(datadir):
     expected_tarballs = [
         {
             'archive': '/root/artanis/artanis-0.2.1.tar.bz2',
             'time': 1495205979,
             'length': 424081,
         },
         {
             'archive': '/root/xboard/winboard/winboard-4_0_0-src.zip',  # noqa
             'time': 898422900,
             'length': 1514448
         },
         {
             'archive': '/root/xboard/xboard-3.6.2.tar.gz',  # noqa
             'time': 869814000,
             'length': 450164,
         },
         {
             'archive': '/root/xboard/xboard-4.0.0.tar.gz',  # noqa
             'time': 898422900,
             'length': 514951,
         },
     ]
 
-    file_structure = json.load(open('swh/lister/gnu/tests/tree.min.json'))
+    file_structure = json.load(open(path.join(datadir, 'tree.min.json')))
     actual_tarballs = find_artifacts(file_structure, '/root/')
     assert actual_tarballs == expected_tarballs
 
 
-def test_find_artifacts():
-    file_structure = json.load(open('swh/lister/gnu/tests/tree.json'))
+def test_find_artifacts(datadir):
+    file_structure = json.load(open(path.join(datadir, 'tree.json')))
     actual_tarballs = find_artifacts(file_structure, '/root/')
     assert len(actual_tarballs) == 42 + 3  # tar + zip
 
 
 def test_check_filename_is_archive():
     for ext in ['abc.xy.zip', 'cvb.zip', 'abc.tar.bz2', 'something.tar']:
         assert check_filename_is_archive(ext) is True
 
     for ext in ['abc.tar.gz.sig', 'abc', 'something.zip2', 'foo.tar.']:
         assert check_filename_is_archive(ext) is False