diff --git a/requirements-test.txt b/requirements-test.txt
index e079f8a..5821059 100644
--- a/requirements-test.txt
+++ b/requirements-test.txt
@@ -1 +1,2 @@
 pytest
+requests_mock
diff --git a/tox.ini b/tox.ini
index 6b8f975..649be35 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,20 +1,21 @@
 [tox]
 envlist=flake8,py3
 
 [testenv:py3]
 deps =
   # the dependency below is needed for now as a workaround for
   #   https://github.com/pypa/pip/issues/6239
   # TODO: remove when this issue is fixed
   swh.core[http] >= 0.0.61
   .[testing]
   pytest-cov
-commands =
-  pytest --cov=swh --cov-branch {posargs}
+commands = pytest --cov={envsitepackagesdir}/swh/loader/pypi \
+         {envsitepackagesdir}/swh/loader/pypi \
+         --cov-branch {posargs}
 
 [testenv:flake8]
 skip_install = true
 deps =
   flake8
 commands =
   {envpython} -m flake8