diff --git a/tox.ini b/tox.ini
--- a/tox.ini
+++ b/tox.ini
@@ -8,7 +8,9 @@
 whitelist_externals = mvn
 commands =
   mvn -f java/server/pom.xml compile assembly:single
-  pytest --cov=swh --cov-branch {posargs}
+  pytest --cov={envsitepackagesdir}/swh/graph \
+         {envsitepackagesdir}/swh/graph \
+         --cov-branch {posargs}
 
 [testenv:flake8]
 skip_install = true