diff --git a/jupyterhub/tests/mocking.py b/jupyterhub/tests/mocking.py
index 9ba425af..368d3cf4 100644
--- a/jupyterhub/tests/mocking.py
+++ b/jupyterhub/tests/mocking.py
@@ -40,7 +40,7 @@ from tornado import gen
 from tornado.concurrent import Future
 from tornado.ioloop import IOLoop
 
-from traitlets import default
+from traitlets import Bool, default
 
 from ..app import JupyterHub
 from ..auth import PAMAuthenticator
@@ -282,12 +282,15 @@ class MockHub(JupyterHub):
             self.db.expire(service)
         return super().init_services()
 
+    clean_users = Bool(True)
+
     def init_db(self):
         """Ensure we start with a clean user list"""
         super().init_db()
-        for user in self.db.query(orm.User):
-            self.db.delete(user)
-        self.db.commit()
+        if self.clean_users:
+            for user in self.db.query(orm.User):
+                self.db.delete(user)
+            self.db.commit()
 
     @gen.coroutine
     def initialize(self, argv=None):
diff --git a/jupyterhub/tests/test_app.py b/jupyterhub/tests/test_app.py
index 759ccafe..87001f2c 100644
--- a/jupyterhub/tests/test_app.py
+++ b/jupyterhub/tests/test_app.py
@@ -206,7 +206,7 @@ def test_resume_spawners(tmpdir, request):
         ssl_enabled = getattr(request.module, "ssl_enabled", False)
         if ssl_enabled:
             kwargs['internal_certs_location'] = str(tmpdir)
-        app = MockHub(**kwargs)
+        app = MockHub(clean_users=False, **kwargs)
         app.config.ConfigurableHTTPProxy.should_start = False
         app.config.ConfigurableHTTPProxy.auth_token = 'unused'
         yield app.initialize([])