diff --git a/swh/auth/pytest_plugin.py b/swh/auth/pytest_plugin.py
--- a/swh/auth/pytest_plugin.py
+++ b/swh/auth/pytest_plugin.py
@@ -59,6 +59,8 @@
         user_info: Dict = USER_INFO,
         raw_realm_public_key: str = RAW_REALM_PUBLIC_KEY,
     ):
+        """Constructor
+        """
         super().__init__(
             server_url=server_url, realm_name=realm_name, client_id=client_id
         )
diff --git a/tox.ini b/tox.ini
--- a/tox.ini
+++ b/tox.ini
@@ -35,3 +35,43 @@
   mypy
 commands =
   mypy swh
+
+# build documentation outside swh-environment using the current
+# git HEAD of swh-docs, is executed on CI for each diff to prevent
+# breaking doc build
+[testenv:sphinx]
+whitelist_externals = make
+usedevelop = true
+extras =
+  django
+  testing
+deps =
+  # fetch and install swh-docs in develop mode
+  -e git+https://forge.softwareheritage.org/source/swh-docs#egg=swh.docs
+
+setenv =
+  SWH_PACKAGE_DOC_TOX_BUILD = 1
+  # turn warnings into errors
+  SPHINXOPTS = -W
+commands =
+  make -I ../.tox/sphinx/src/swh-docs/swh/ -C docs
+
+
+# build documentation only inside swh-environment using local state
+# of swh-docs package
+[testenv:sphinx-dev]
+whitelist_externals = make
+usedevelop = true
+extras =
+  django
+  testing
+deps =
+  # install swh-docs in develop mode
+  -e ../swh-docs
+
+setenv =
+  SWH_PACKAGE_DOC_TOX_BUILD = 1
+  # turn warnings into errors
+  SPHINXOPTS = -W
+commands =
+  make -I ../.tox/sphinx-dev/src/swh-docs/swh/ -C docs