let's include the test in the PR, shall we?

src/ZEO/tests/test_client_credentials.py

+"""Clients can pass credentials to a server.
+
+This is an experimental feature to enable server authentication and
+authorization.
+"""
+from zope.testing import setupstack
+import unittest
+
+import ZEO.StorageServer
+
+class ClientAuthTests(setupstack.TestCase):
+
+    def setUp(self):
+        self.setUpDirectory()
+        self.__register = ZEO.StorageServer.ZEOStorage.register
+
+    def tearDown(self):
+        ZEO.StorageServer.ZEOStorage.register = self.__register
+
+    def test_passing_credentials(self):
+
+        # First, we'll temporarily swap the storage server register
+        # method with one that let's is see credentials that were passed:
+
+        creds_log = []
+
+        def register(zs, storage_id, read_only, credentials=self):
+            creds_log.append(credentials)
+            return self.__register(zs, storage_id, read_only)
+
+        ZEO.StorageServer.ZEOStorage.register = register
+
+        # Now start an in process server
+        addr, stop = ZEO.server()
+
+        # If we connect, without providing credentials, then no
+        # credentials will be passed to register:
+
+        client = ZEO.client(addr)
+
+        self.assertEqual(creds_log, [self])
+        client.close()
+        creds_log.pop()
+
+        # But if we pass credentials, they'll be passed to register:
+        creds = dict(user='me', password='123')
+        client = ZEO.client(addr, credentials=creds)
+        self.assertEqual(creds_log, [creds])
+        client.close()
+
+        stop()
+
+
+def test_suite():
+    return unittest.makeSuite(ClientAuthTests)
+