diff --git a/resources/loader.yml b/resources/loader.yml
new file mode 100644
index 0000000..0c9a3fe
--- /dev/null
+++ b/resources/loader.yml
@@ -0,0 +1,3 @@
+storage:
+  cls: memory
+  args: {}
diff --git a/swh/loader/package/tests/test_pypi.py b/swh/loader/package/tests/test_pypi.py
index 5864b01..ea3dcb4 100644
--- a/swh/loader/package/tests/test_pypi.py
+++ b/swh/loader/package/tests/test_pypi.py
@@ -1,41 +1,53 @@
 # 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 os
+import pytest
+
+from swh.loader.package.pypi import PyPILoader
+
 # scenario
 
 # configuration error #
 
-# badly configured loader fails
+def test_badly_configured_loader_raise():
+    """Badly configured loader should raise"""
+    assert 'SWH_CONFIG_FILENAME' in os.environ  # cf. tox.ini
+    del os.environ['SWH_CONFIG_FILENAME']
+    with pytest.raises(ValueError) as e:
+        PyPILoader(url='some-url')
+
+    assert 'Misconfiguration' in e.value.args[0]
 
 # "edge" cases (for the same origin) #
 
 # no release artifact:
 # {visit full, status: uneventful, no contents, etc...}
 
 # problem during loading:
 # {visit: partial, status: uneventful, no snapshot}
 
 # problem during loading: failure early enough in between swh contents...
 # some contents (contents, directories, etc...) have been written in storage
 # {visit: partial, status: eventful, no snapshot}
 
 # problem during loading: failure late enough we can have snapshots (some
 # revisions are written in storage already)
 # {visit: partial, status: eventful, snapshot}
 
 # "normal" cases (for the same origin) #
 
 # release artifact, no prior visit
 # {visit full, status eventful, snapshot}
 
 # release artifact, no new artifact
 # {visit full, status uneventful, same snapshot as before}
 
 # release artifact, new artifact
 # {visit full, status full, new snapshot with shared history as prior snapshot}
 
 # release artifact, old artifact with different checksums
 # {visit full, status full, new snapshot with shared history and some new
 # different history}
diff --git a/tox.ini b/tox.ini
index 0fb07c6..8e4539e 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,16 +1,18 @@
 [tox]
 envlist=flake8,py3
 
 [testenv:py3]
 deps =
   .[testing]
   pytest-cov
+setenv =
+   SWH_CONFIG_FILENAME = ./resources/loader.yml
 commands =
   pytest --cov=swh --cov-branch {posargs}
 
 [testenv:flake8]
 skip_install = true
 deps =
   flake8
 commands =
   {envpython} -m flake8