diff --git a/cloudbaseinit/tests/utils/test_log.py b/cloudbaseinit/tests/utils/test_log.py
index 05e3c354..d5c03c1b 100644
--- a/cloudbaseinit/tests/utils/test_log.py
+++ b/cloudbaseinit/tests/utils/test_log.py
@@ -14,51 +14,68 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import importlib
 import mock
 import unittest
 
 from oslo.config import cfg
 
-from cloudbaseinit.utils import log
-
 CONF = cfg.CONF
 
 
 class SerialPortHandlerTests(unittest.TestCase):
-    @mock.patch('serial.Serial')
-    def setUp(self, mock_Serial):
+    def setUp(self):
+        self._serial = mock.MagicMock()
+        self._module_patcher = mock.patch.dict(
+            'sys.modules',
+            {'serial': self._serial})
+
+        self._module_patcher.start()
+
+        self.log = importlib.import_module("cloudbaseinit.utils.log")
+
         CONF.set_override('logging_serial_port_settings', "COM1,115200,N,8")
-        self._serial_port_handler = log.SerialPortHandler()
+        self._serial_port_handler = self.log.SerialPortHandler()
         self._serial_port_handler._port = mock.MagicMock()
 
-    @mock.patch('serial.Serial')
-    def test_init(self, mock_Serial):
-        mock_Serial().isOpen.return_value = False
-        log.SerialPortHandler()
+    def tearDown(self):
+        self._module_patcher.stop()
+
+    def test_init(self):
+        mock_Serial = self._serial.Serial
+        mock_Serial.return_value.isOpen.return_value = False
+
+        self.log.SerialPortHandler()
+
         mock_Serial.assert_called_with(bytesize=8, baudrate=115200,
                                        port='COM1', parity='N')
-        mock_Serial().isOpen.assert_called_once_with()
-        mock_Serial().open.assert_called_once_with()
+        mock_Serial.return_value.isOpen.assert_called_with()
+        mock_Serial.return_value.open.assert_called_once_with()
 
     def test_close(self):
         self._serial_port_handler._port.isOpen.return_value = True
+
         self._serial_port_handler.close()
+
         self._serial_port_handler._port.isOpen.assert_called_once_with()
         self._serial_port_handler._port.close.assert_called_once_with()
 
+    @mock.patch('cloudbaseinit.openstack.common.log.setup')
+    @mock.patch('cloudbaseinit.openstack.common.log.getLogger')
+    @mock.patch('cloudbaseinit.utils.log.SerialPortHandler')
+    @mock.patch('cloudbaseinit.openstack.common.log.ContextFormatter')
+    def test_setup(self, mock_ContextFormatter, mock_SerialPortHandler,
+                   mock_getLogger, mock_setup):
 
-@mock.patch('cloudbaseinit.openstack.common.log.setup')
-@mock.patch('cloudbaseinit.openstack.common.log.getLogger')
-@mock.patch('cloudbaseinit.utils.log.SerialPortHandler')
-@mock.patch('cloudbaseinit.openstack.common.log.ContextFormatter')
-def test_setup(mock_ContextFormatter, mock_SerialPortHandler, mock_getLogger,
-               mock_setup):
-    log.setup(product_name='fake name')
-    mock_setup.assert_called_once_with('fake name')
-    mock_getLogger.assert_called_once_with('fake name')
-    mock_getLogger().logger.addHandler.assert_called_once_with(
-        mock_SerialPortHandler())
-    mock_ContextFormatter.assert_called_once_with(
-        project='fake name', datefmt=CONF.log_date_format)
-    mock_SerialPortHandler().setFormatter.assert_called_once_with(
-        mock_ContextFormatter())
+        self.log.setup(product_name='fake name')
+
+        mock_setup.assert_called_once_with('fake name')
+        mock_getLogger.assert_called_once_with('fake name')
+        mock_getLogger().logger.addHandler.assert_called_once_with(
+            mock_SerialPortHandler())
+
+        mock_ContextFormatter.assert_called_once_with(
+            project='fake name', datefmt=CONF.log_date_format)
+
+        mock_SerialPortHandler().setFormatter.assert_called_once_with(
+            mock_ContextFormatter())