diff --git a/swh/loader/package/tests/conftest.py b/swh/loader/package/tests/conftest.py
index 0349583..7c359b4 100644
--- a/swh/loader/package/tests/conftest.py
+++ b/swh/loader/package/tests/conftest.py
@@ -1,84 +1,99 @@
 # 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 logging
 import os
 import re
 import pytest
 
+from functools import partial
 from os import path
 from urllib.parse import urlparse
 
 from .common import DATADIR
 
 
 logger = logging.getLogger(__name__)
 
 
 @pytest.fixture
 def swh_config(monkeypatch):
     conffile = os.path.join(DATADIR, 'loader.yml')
     monkeypatch.setenv('SWH_CONFIG_FILENAME', conffile)
     return conffile
 
 
-def get_response_cb(request, context):
+def get_response_cb(request, context, ignore_urls=[]):
     """Mount point callback to fetch on disk the content of a request
 
     This is meant to be used as 'body' argument of the requests_mock.get()
     method.
 
     It will look for files on the local filesystem based on the requested URL,
     using the following rules:
 
     - files are searched in the DATADIR/<hostname> directory
 
     - the local file name is the path part of the URL with path hierarchy
       markers (aka '/') replaced by '_'
 
     Eg. if you use the requests_mock fixture in your test file as:
 
         requests_mock.get('https://nowhere.com', body=get_response_cb)
         # or even
         requests_mock.get(re.compile('https://'), body=get_response_cb)
 
     then a call requests.get like:
 
         requests.get('https://nowhere.com/path/to/resource')
 
     will look the content of the response in:
 
         DATADIR/resources/nowhere.com/path_to_resource
 
     Args:
         request (requests.Request): Object requests
         context (requests.Context): Object holding response metadata
                                     information (status_code, headers, etc...)
+        ignore_urls (List): urls whose status response should be 404 even if
+                            the local file exists
 
     Returns:
-        File descriptor on the on disk file to read from the test context
+        Optional[FileDescriptor] on the on disk file to read from the test
+        context
 
     """
     logger.debug('get_response_cb(%s, %s)', request, context)
     url = urlparse(request.url)
+    if url in ignore_urls:
+        context.status_code = 404
+        return None
     dirname = url.hostname  # pypi.org | files.pythonhosted.org
     # url.path: pypi/<project>/json -> local file: pypi_<project>_json
     filename = url.path[1:]
     if filename.endswith('/'):
         filename = filename[:-1]
     filename = filename.replace('/', '_')
     filepath = path.join(DATADIR, dirname, filename)
     if not path.isfile(filepath):
         context.status_code = 404
         return None
     fd = open(filepath, 'rb')
     context.headers['content-length'] = str(path.getsize(filepath))
     return fd
 
 
-@pytest.fixture
-def local_get(requests_mock):
-    requests_mock.get(re.compile('https://'), body=get_response_cb)
-    return requests_mock
+def local_get_factory(ignore_urls=[]):
+    @pytest.fixture
+    def local_get(requests_mock):
+        cb = partial(get_response_cb, ignore_urls=ignore_urls)
+        requests_mock.get(re.compile('https://'), body=cb)
+
+        return requests_mock
+
+    return local_get
+
+
+local_get = local_get_factory([])