PYTHON-4209 Fix test for ensure that no error is raised for unknown auth mechanism

test/mockupdb/test_handshake.py

@@ -218,50 +218,19 @@ def test_client_handshake_saslSupportedMechs(self):
                     request.ok(
                         "ismaster",
                         True,
-                        saslSupportedMechs=["SCRAM-SHA-256"],
+                        # Unsupported auth mech should be ignored.
+                        saslSupportedMechs=["SCRAM-SHA-256", "does_not_exist"],
                         speculativeAuthenticate=auth,
                         minWireVersion=2,
                         maxWireVersion=MIN_SUPPORTED_WIRE_VERSION,
                     )
                     # Authentication should immediately fail with:
                     # OperationFailure: Server returned an invalid nonce.
-                    with self.assertRaises(OperationFailure):
+                    with self.assertRaises(OperationFailure) as cm:
                         future()
+                    self.assertEqual(str(cm.exception), "Server returned an invalid nonce.")
                     return
 
-    def test_client_handshake_saslSupportedMechs_unknown(self):
-        server = MockupDB()
-        server.run()
-        self.addCleanup(server.stop)
-
-        primary_response = OpReply(
-            "ismaster",
-            True,
-            minWireVersion=2,
-            maxWireVersion=MIN_SUPPORTED_WIRE_VERSION,
-            saslSupportedMechs=["SCRAM-SHA-256", "does_not_exist"],
-        )
-        client = MongoClient(
-            server.uri, authmechanism="PLAIN", username="username", password="password"
-        )
-
-        self.addCleanup(client.close)
-
-        # New monitoring connections send data during handshake.
-        heartbeat = server.receives("ismaster")
-        heartbeat.ok(primary_response)
-
-        future = go(client.db.command, "whatever")
-        for request in server:
-            if request.matches("ismaster"):
-                request.ok(primary_response)
-            elif request.matches("saslStart"):
-                request.ok("saslStart", True, conversationId=1, payload=b"", done=True, ok=1)
-            else:
-                request.ok()
-                future()
-                return
-
     def test_handshake_load_balanced(self):
         self.hello_with_option_helper(OpMsg, loadBalanced=True)
         with self.assertRaisesRegex(AssertionError, "does not match"):