diff --git a/test/test_event_loggers.py b/test/test_event_loggers.py
new file mode 100644
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+++ b/test/test_event_loggers.py
@@ -0,0 +1,374 @@
+# Copyright 2026-present MongoDB, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Tests for pymongo.event_loggers."""
+from __future__ import annotations
+
+import sys
+from unittest.mock import MagicMock, patch
+
+sys.path[0:0] = [""]
+
+from test import unittest
+
+from pymongo.event_loggers import (
+    CommandLogger,
+    ConnectionPoolLogger,
+    HeartbeatLogger,
+    ServerLogger,
+    TopologyLogger,
+)
+
+
+class TestCommandLogger(unittest.TestCase):
+    def setUp(self):
+        self.logger = CommandLogger()
+
+    def test_started_logs_info(self):
+        event = MagicMock()
+        event.command_name = "find"
+        event.request_id = 42
+        event.connection_id = ("localhost", 27017)
+        with self.assertLogs(level="INFO") as logs:
+            self.logger.started(event)
+        log = logs.records[0].getMessage()
+        self.assertIn("find", log)
+        self.assertIn("42", log)
+        self.assertIn("started", log)
+
+    def test_succeeded_logs_info(self):
+        event = MagicMock()
+        event.command_name = "insert"
+        event.request_id = 7
+        event.connection_id = ("localhost", 27017)
+        event.duration_micros = 500
+        with self.assertLogs(level="INFO") as logs:
+            self.logger.succeeded(event)
+        log = logs.records[0].getMessage()
+        self.assertIn("insert", log)
+        self.assertIn("7", log)
+        self.assertIn("500", log)
+        self.assertIn("microseconds", log)
+        self.assertIn("succeeded", log)
+
+    def test_failed_logs_info(self):
+        event = MagicMock()
+        event.command_name = "delete"
+        event.request_id = 3
+        event.connection_id = ("localhost", 27017)
+        event.duration_micros = 300
+        with self.assertLogs(level="INFO") as logs:
+            self.logger.failed(event)
+        log = logs.records[0].getMessage()
+        self.assertIn("delete", log)
+        self.assertIn("3", log)
+        self.assertIn("300", log)
+        self.assertIn("microseconds", log)
+        self.assertIn("failed", log)
+
+
+class TestServerLogger(unittest.TestCase):
+    def setUp(self):
+        self.logger = ServerLogger()
+
+    def test_opened_logs_info(self):
+        event = MagicMock()
+        event.server_address = ("host1", 27017)
+        event.topology_id = "topology-abc"
+        with self.assertLogs(level="INFO") as logs:
+            self.logger.opened(event)
+        log = logs.records[0].getMessage()
+        self.assertIn("host1", log)
+        self.assertIn("topology-abc", log)
+
+    def test_closed_logs_warning(self):
+        event = MagicMock()
+        event.server_address = ("host1", 27017)
+        event.topology_id = "topology-abc"
+        with self.assertLogs(level="WARNING") as logs:
+            self.logger.closed(event)
+        log = logs.records[0].getMessage()
+        self.assertIn("host1", log)
+        self.assertIn("topology-abc", log)
+
+    def test_description_changed_logs_when_type_changes(self):
+        event = MagicMock()
+        event.server_address = ("host1", 27017)
+        event.previous_description.server_type = 1
+        event.previous_description.server_type_name = "Unknown"
+        event.new_description.server_type = 2
+        event.new_description.server_type_name = "Standalone"
+        with self.assertLogs(level="INFO") as logs:
+            self.logger.description_changed(event)
+        log = logs.records[0].getMessage()
+        self.assertIn("Unknown", log)
+        self.assertIn("Standalone", log)
+
+    def test_description_changed_no_log_when_type_same(self):
+        event = MagicMock()
+        event.previous_description.server_type = 2
+        event.new_description.server_type = 2
+        with patch("logging.info") as mock_info:
+            self.logger.description_changed(event)
+        mock_info.assert_not_called()
+
+
+class TestHeartbeatLogger(unittest.TestCase):
+    def setUp(self):
+        self.logger = HeartbeatLogger()
+
+    def test_started_logs_info(self):
+        event = MagicMock()
+        event.connection_id = ("mongo.host", 27017)
+        with self.assertLogs(level="INFO") as logs:
+            self.logger.started(event)
+        log = logs.records[0].getMessage()
+        self.assertIn("mongo.host", log)
+
+    def test_succeeded_logs_info(self):
+        event = MagicMock()
+        event.connection_id = ("mongo.host", 27017)
+        event.reply.document = {"ok": 1, "maxWireVersion": 17}
+        with self.assertLogs(level="INFO") as logs:
+            self.logger.succeeded(event)
+        log = logs.records[0].getMessage()
+        self.assertIn("mongo.host", log)
+        self.assertIn("succeeded", log)
+        self.assertIn("maxWireVersion", log)
+
+    def test_failed_logs_warning(self):
+        event = MagicMock()
+        event.connection_id = ("mongo.host", 27017)
+        event.reply = TimeoutError("timed out")
+        with self.assertLogs(level="WARNING") as logs:
+            self.logger.failed(event)
+        log = logs.records[0].getMessage()
+        self.assertIn("mongo.host", log)
+        self.assertIn("failed", log)
+        self.assertIn("timed out", log)
+
+
+class TestTopologyLogger(unittest.TestCase):
+    def setUp(self):
+        self.logger = TopologyLogger()
+
+    def test_opened_logs_info(self):
+        event = MagicMock()
+        event.topology_id = "topo-1"
+        with self.assertLogs(level="INFO") as logs:
+            self.logger.opened(event)
+        log = logs.records[0].getMessage()
+        self.assertIn("topo-1", log)
+        self.assertIn("opened", log)
+
+    def test_closed_logs_info(self):
+        event = MagicMock()
+        event.topology_id = "topo-1"
+        with self.assertLogs(level="INFO") as logs:
+            self.logger.closed(event)
+        log = logs.records[0].getMessage()
+        self.assertIn("topo-1", log)
+        self.assertIn("closed", log)
+
+    def test_description_changed_always_logs_update(self):
+        event = MagicMock()
+        event.topology_id = "topo-1"
+        event.previous_description.topology_type = 1
+        event.new_description.topology_type = 1
+        event.new_description.has_writable_server.return_value = True
+        event.new_description.has_readable_server.return_value = True
+        with self.assertLogs(level="INFO") as logs:
+            self.logger.description_changed(event)
+        messages = [r.getMessage() for r in logs.records]
+        self.assertTrue(any("updated" in m for m in messages))
+        self.assertTrue(any("topo-1" in m for m in messages))
+
+    def test_description_changed_logs_type_change(self):
+        event = MagicMock()
+        event.topology_id = "topo-2"
+        event.previous_description.topology_type = 0
+        event.previous_description.topology_type_name = "Unknown"
+        event.new_description.topology_type = 1
+        event.new_description.topology_type_name = "Single"
+        event.new_description.has_writable_server.return_value = True
+        event.new_description.has_readable_server.return_value = True
+        with self.assertLogs(level="INFO") as logs:
+            self.logger.description_changed(event)
+        messages = [r.getMessage() for r in logs.records]
+        self.assertTrue(any("Unknown" in m and "Single" in m for m in messages))
+
+    def test_description_changed_no_type_change_log_when_same(self):
+        event = MagicMock()
+        event.topology_id = "topo-1"
+        event.previous_description.topology_type = 1
+        event.new_description.topology_type = 1
+        event.new_description.has_writable_server.return_value = True
+        event.new_description.has_readable_server.return_value = True
+        with self.assertLogs(level="INFO") as logs:
+            self.logger.description_changed(event)
+        messages = [r.getMessage() for r in logs.records]
+        self.assertFalse(any("changed type" in m for m in messages))
+
+    def test_description_changed_warns_no_writable_server(self):
+        event = MagicMock()
+        event.previous_description.topology_type = 1
+        event.new_description.topology_type = 1
+        event.new_description.has_writable_server.return_value = False
+        event.new_description.has_readable_server.return_value = True
+        with self.assertLogs(level="WARNING") as logs:
+            self.logger.description_changed(event)
+        messages = [r.getMessage() for r in logs.records]
+        self.assertTrue(any("writable" in m for m in messages))
+
+    def test_description_changed_warns_no_readable_server(self):
+        event = MagicMock()
+        event.previous_description.topology_type = 1
+        event.new_description.topology_type = 1
+        event.new_description.has_writable_server.return_value = True
+        event.new_description.has_readable_server.return_value = False
+        with self.assertLogs(level="WARNING") as logs:
+            self.logger.description_changed(event)
+        messages = [r.getMessage() for r in logs.records]
+        self.assertTrue(any("readable" in m for m in messages))
+
+    def test_description_changed_warns_both_unavailable(self):
+        event = MagicMock()
+        event.previous_description.topology_type = 1
+        event.new_description.topology_type = 1
+        event.new_description.has_writable_server.return_value = False
+        event.new_description.has_readable_server.return_value = False
+        with self.assertLogs(level="WARNING") as logs:
+            self.logger.description_changed(event)
+        warning_messages = [r.getMessage() for r in logs.records if r.levelname == "WARNING"]
+        self.assertEqual(len(warning_messages), 2)
+
+
+class TestConnectionPoolLogger(unittest.TestCase):
+    def setUp(self):
+        self.logger = ConnectionPoolLogger()
+
+    def test_pool_created(self):
+        event = MagicMock()
+        event.address = ("localhost", 27017)
+        with self.assertLogs(level="INFO") as logs:
+            self.logger.pool_created(event)
+        log = logs.records[0].getMessage()
+        self.assertIn("pool created", log)
+        self.assertIn("localhost", log)
+
+    def test_pool_ready(self):
+        event = MagicMock()
+        event.address = ("localhost", 27017)
+        with self.assertLogs(level="INFO") as logs:
+            self.logger.pool_ready(event)
+        log = logs.records[0].getMessage()
+        self.assertIn("pool ready", log)
+        self.assertIn("localhost", log)
+
+    def test_pool_cleared(self):
+        event = MagicMock()
+        event.address = ("localhost", 27017)
+        with self.assertLogs(level="INFO") as logs:
+            self.logger.pool_cleared(event)
+        log = logs.records[0].getMessage()
+        self.assertIn("pool cleared", log)
+        self.assertIn("localhost", log)
+
+    def test_pool_closed(self):
+        event = MagicMock()
+        event.address = ("localhost", 27017)
+        with self.assertLogs(level="INFO") as logs:
+            self.logger.pool_closed(event)
+        log = logs.records[0].getMessage()
+        self.assertIn("pool closed", log)
+        self.assertIn("localhost", log)
+
+    def test_connection_created(self):
+        event = MagicMock()
+        event.address = ("localhost", 27017)
+        event.connection_id = 5
+        with self.assertLogs(level="INFO") as logs:
+            self.logger.connection_created(event)
+        log = logs.records[0].getMessage()
+        self.assertIn("connection created", log)
+        self.assertIn("5", log)
+        self.assertIn("localhost", log)
+
+    def test_connection_ready(self):
+        event = MagicMock()
+        event.address = ("localhost", 27017)
+        event.connection_id = 5
+        with self.assertLogs(level="INFO") as logs:
+            self.logger.connection_ready(event)
+        log = logs.records[0].getMessage()
+        self.assertIn("connection setup succeeded", log)
+        self.assertIn("5", log)
+
+    def test_connection_closed(self):
+        event = MagicMock()
+        event.address = ("localhost", 27017)
+        event.connection_id = 5
+        event.reason = "stale"
+        with self.assertLogs(level="INFO") as logs:
+            self.logger.connection_closed(event)
+        log = logs.records[0].getMessage()
+        self.assertIn("connection closed", log)
+        self.assertIn("5", log)
+        self.assertIn("stale", log)
+
+    def test_connection_check_out_started(self):
+        event = MagicMock()
+        event.address = ("localhost", 27017)
+        with self.assertLogs(level="INFO") as logs:
+            self.logger.connection_check_out_started(event)
+        log = logs.records[0].getMessage()
+        self.assertIn("check out started", log)
+        self.assertIn("localhost", log)
+
+    def test_connection_check_out_failed(self):
+        event = MagicMock()
+        event.address = ("localhost", 27017)
+        event.reason = "timeout"
+        with self.assertLogs(level="INFO") as logs:
+            self.logger.connection_check_out_failed(event)
+        log = logs.records[0].getMessage()
+        self.assertIn("check out failed", log)
+        self.assertIn("timeout", log)
+        self.assertIn("localhost", log)
+
+    def test_connection_checked_out(self):
+        event = MagicMock()
+        event.address = ("localhost", 27017)
+        event.connection_id = 3
+        with self.assertLogs(level="INFO") as logs:
+            self.logger.connection_checked_out(event)
+        log = logs.records[0].getMessage()
+        self.assertIn("checked out", log)
+        self.assertIn("3", log)
+        self.assertIn("localhost", log)
+
+    def test_connection_checked_in(self):
+        event = MagicMock()
+        event.address = ("localhost", 27017)
+        event.connection_id = 3
+        with self.assertLogs(level="INFO") as logs:
+            self.logger.connection_checked_in(event)
+        log = logs.records[0].getMessage()
+        self.assertIn("checked into", log)
+        self.assertIn("3", log)
+        self.assertIn("localhost", log)
+
+
+if __name__ == "__main__":
+    unittest.main()