diff --git a/tests/test_client.py b/tests/test_client.py
index ce23cae..6722225 100644
--- a/tests/test_client.py
+++ b/tests/test_client.py
@@ -1,14 +1,17 @@
 """Tests for the Victron Energy VRM API client."""
 
 import logging
+import unittest.mock
 
 import aiohttp
 import pytest
 import random
 
 from victron_vrm import VictronVRMClient
-from victron_vrm.exceptions import VictronVRMError, AuthorizationError
+from victron_vrm.exceptions import VictronVRMError, AuthorizationError, NotFoundError, ClientError
 from victron_vrm.models import Site
+from victron_vrm.models.auth import AuthToken
+from victron_vrm.mqtt import VRMMQTTClient
 
 # Set up logging
 logging.basicConfig(
@@ -21,6 +24,34 @@
 AUTH_DEMO_URL = "https://vrmapi.victronenergy.com/v2/auth/loginAsDemo"
 
 
+# Helper classes for mocking
+class _MockUser:
+    """Mock user for testing."""
+    email = "test@example.com"
+
+
+class _MockSite:
+    """Mock site for testing."""
+    identifier = "test-vrm-id"
+    mqtt_hostname = "mqtt.victronenergy.com"
+
+
+class _MockSiteNoHostname:
+    """Mock site without MQTT hostname for testing."""
+    identifier = "test-vrm-id"
+    mqtt_hostname = None
+
+
+def _create_mock_token():
+    """Create a mock auth token for testing."""
+    return AuthToken(
+        access_token="mock_access_token",
+        token_type="Bearer",
+        expires_in=3600,
+        scope="read"
+    )
+
+
 @pytest.fixture(scope="session")
 async def demo_token():
     """Get a demo token for testing (session-scoped to avoid 429s)."""
@@ -373,3 +404,72 @@ async def test_stats_false_to_none_transformation(vrm_client):
     except VictronVRMError as e:
         logger.warning(f"Error in mock test: {e}")
         pytest.skip(f"Error in mock test: {e}")
+
+
+@pytest.mark.asyncio
+async def test_get_mqtt_client_for_installation_success():
+    """Test getting MQTT client for a valid installation."""
+    # Create a mock client without needing actual network access
+    async with VictronVRMClient(token="mock_token", token_type="Bearer") as client:
+        async def mock_gather(*args):
+            return _create_mock_token(), _MockUser(), [_MockSite()]
+        
+        # Mock asyncio.gather to avoid actual API calls
+        with unittest.mock.patch("asyncio.gather", side_effect=mock_gather):
+            # Get MQTT client
+            mqtt_client = await client.get_mqtt_client_for_installation(67890)
+            
+            # Verify the client is properly configured
+            assert mqtt_client is not None
+            assert isinstance(mqtt_client, VRMMQTTClient)
+            
+            # Verify client attributes
+            assert mqtt_client.host == "mqtt.victronenergy.com"
+            assert mqtt_client.username == "test@example.com"
+            assert mqtt_client.password == "Bearer mock_access_token"
+            assert mqtt_client.installation_id == "test-vrm-id"
+            
+            logger.info("Successfully created MQTT client with mocked data")
+
+
+@pytest.mark.asyncio
+async def test_get_mqtt_client_for_installation_not_found():
+    """Test getting MQTT client for a non-existent installation."""
+    # Create a mock client
+    async with VictronVRMClient(token="mock_token", token_type="Bearer") as client:
+        async def mock_gather(*args):
+            # Return empty list for installations
+            return _create_mock_token(), _MockUser(), []
+        
+        # Mock asyncio.gather to return empty installations list
+        with unittest.mock.patch("asyncio.gather", side_effect=mock_gather):
+            # Should raise NotFoundError
+            with pytest.raises(NotFoundError) as exc_info:
+                await client.get_mqtt_client_for_installation(999999999)
+            
+            # Verify the error message
+            assert "not found" in str(exc_info.value).lower()
+            assert "999999999" in str(exc_info.value)
+            
+            logger.info("NotFoundError correctly raised for invalid installation ID")
+
+
+@pytest.mark.asyncio
+async def test_get_mqtt_client_for_installation_missing_hostname():
+    """Test getting MQTT client for installation without MQTT hostname."""
+    # Create a mock client
+    async with VictronVRMClient(token="mock_token", token_type="Bearer") as client:
+        async def mock_gather(*args):
+            return _create_mock_token(), _MockUser(), [_MockSiteNoHostname()]
+        
+        # Mock asyncio.gather
+        with unittest.mock.patch("asyncio.gather", side_effect=mock_gather):
+            # Should raise ClientError
+            with pytest.raises(ClientError) as exc_info:
+                await client.get_mqtt_client_for_installation(67890)
+            
+            # Verify the error message
+            assert "mqtt hostname" in str(exc_info.value).lower()
+            assert "67890" in str(exc_info.value)
+            
+            logger.info("ClientError correctly raised for installation without MQTT hostname")