diff --git a/tests/server/events/test_inmemory_queue_manager.py b/tests/server/events/test_inmemory_queue_manager.py
new file mode 100644
index 00000000..8371903c
--- /dev/null
+++ b/tests/server/events/test_inmemory_queue_manager.py
@@ -0,0 +1,151 @@
+import asyncio
+
+from unittest.mock import MagicMock
+
+import pytest
+
+from a2a.server.events import InMemoryQueueManager
+from a2a.server.events.event_queue import EventQueue
+from a2a.server.events.queue_manager import (
+    NoTaskQueue,
+    TaskQueueExists,
+)
+
+
+class TestInMemoryQueueManager:
+    @pytest.fixture
+    def queue_manager(self):
+        """Fixture to create a fresh InMemoryQueueManager for each test."""
+        manager = InMemoryQueueManager()
+        return manager
+
+    @pytest.fixture
+    def event_queue(self):
+        """Fixture to create a mock EventQueue."""
+        queue = MagicMock(spec=EventQueue)
+        # Mock the tap method to return itself
+        queue.tap.return_value = queue
+        return queue
+
+    @pytest.mark.asyncio
+    async def test_init(self, queue_manager):
+        """Test that the InMemoryQueueManager initializes with empty task queue and a lock."""
+        assert queue_manager._task_queue == {}
+        assert isinstance(queue_manager._lock, asyncio.Lock)
+
+    @pytest.mark.asyncio
+    async def test_add_new_queue(self, queue_manager, event_queue):
+        """Test adding a new queue to the manager."""
+        task_id = 'test_task_id'
+        await queue_manager.add(task_id, event_queue)
+        assert queue_manager._task_queue[task_id] == event_queue
+
+    @pytest.mark.asyncio
+    async def test_add_existing_queue(self, queue_manager, event_queue):
+        """Test adding a queue with an existing task_id raises TaskQueueExists."""
+        task_id = 'test_task_id'
+        await queue_manager.add(task_id, event_queue)
+
+        with pytest.raises(TaskQueueExists):
+            await queue_manager.add(task_id, event_queue)
+
+    @pytest.mark.asyncio
+    async def test_get_existing_queue(self, queue_manager, event_queue):
+        """Test getting an existing queue returns the queue."""
+        task_id = 'test_task_id'
+        await queue_manager.add(task_id, event_queue)
+
+        result = await queue_manager.get(task_id)
+        assert result == event_queue
+
+    @pytest.mark.asyncio
+    async def test_get_nonexistent_queue(self, queue_manager):
+        """Test getting a nonexistent queue returns None."""
+        result = await queue_manager.get('nonexistent_task_id')
+        assert result is None
+
+    @pytest.mark.asyncio
+    async def test_tap_existing_queue(self, queue_manager, event_queue):
+        """Test tapping an existing queue returns the tapped queue."""
+        task_id = 'test_task_id'
+        await queue_manager.add(task_id, event_queue)
+
+        result = await queue_manager.tap(task_id)
+        assert result == event_queue
+        event_queue.tap.assert_called_once()
+
+    @pytest.mark.asyncio
+    async def test_tap_nonexistent_queue(self, queue_manager):
+        """Test tapping a nonexistent queue returns None."""
+        result = await queue_manager.tap('nonexistent_task_id')
+        assert result is None
+
+    @pytest.mark.asyncio
+    async def test_close_existing_queue(self, queue_manager, event_queue):
+        """Test closing an existing queue removes it from the manager."""
+        task_id = 'test_task_id'
+        await queue_manager.add(task_id, event_queue)
+
+        await queue_manager.close(task_id)
+        assert task_id not in queue_manager._task_queue
+
+    @pytest.mark.asyncio
+    async def test_close_nonexistent_queue(self, queue_manager):
+        """Test closing a nonexistent queue raises NoTaskQueue."""
+        with pytest.raises(NoTaskQueue):
+            await queue_manager.close('nonexistent_task_id')
+
+    @pytest.mark.asyncio
+    async def test_create_or_tap_new_queue(self, queue_manager):
+        """Test create_or_tap with a new task_id creates and returns a new queue."""
+        task_id = 'test_task_id'
+
+        result = await queue_manager.create_or_tap(task_id)
+        assert isinstance(result, EventQueue)
+        assert queue_manager._task_queue[task_id] == result
+
+    @pytest.mark.asyncio
+    async def test_create_or_tap_existing_queue(
+        self, queue_manager, event_queue
+    ):
+        """Test create_or_tap with an existing task_id taps and returns the existing queue."""
+        task_id = 'test_task_id'
+        await queue_manager.add(task_id, event_queue)
+
+        result = await queue_manager.create_or_tap(task_id)
+
+        assert result == event_queue
+        event_queue.tap.assert_called_once()
+
+    @pytest.mark.asyncio
+    async def test_concurrency(self, queue_manager):
+        """Test concurrent access to the queue manager."""
+
+        async def add_task(task_id):
+            queue = EventQueue()
+            await queue_manager.add(task_id, queue)
+            return task_id
+
+        async def get_task(task_id):
+            return await queue_manager.get(task_id)
+
+        # Create 10 different task IDs
+        task_ids = [f'task_{i}' for i in range(10)]
+
+        # Add tasks concurrently
+        add_tasks = [add_task(task_id) for task_id in task_ids]
+        added_task_ids = await asyncio.gather(*add_tasks)
+
+        # Verify all tasks were added
+        assert set(added_task_ids) == set(task_ids)
+
+        # Get tasks concurrently
+        get_tasks = [get_task(task_id) for task_id in task_ids]
+        queues = await asyncio.gather(*get_tasks)
+
+        # Verify all queues are not None
+        assert all(queue is not None for queue in queues)
+
+        # Verify all tasks are in the manager
+        for task_id in task_ids:
+            assert task_id in queue_manager._task_queue