diff --git a/Makefile b/Makefile
index 182bdae..f8df749 100644
--- a/Makefile
+++ b/Makefile
@@ -55,6 +55,9 @@ docs:
 	cd docs
 	make html
 
+sh:  # open subshell with default test config
+	$$SHELL;
+
 linkcheck:
 	sphinx-build -W -b linkcheck ./docs/ ./docs/_build/linkcheck/
 
diff --git a/tests/storage/dav/__init__.py b/tests/storage/dav/__init__.py
index c9780b9..76bba50 100644
--- a/tests/storage/dav/__init__.py
+++ b/tests/storage/dav/__init__.py
@@ -13,7 +13,7 @@ from vdirsyncer.storage.base import Item
 from .. import StorageTests
 
 
-dav_server = os.environ.get('DAV_SERVER', '').strip() or 'radicale'
+dav_server = os.environ['DAV_SERVER']
 
 
 def _get_server_mixin(server_name):