diff --git a/tests/test_wakatime_offlinequeue.py b/tests/test_wakatime_offlinequeue.py
new file mode 100644
index 0000000..31e8da5
--- /dev/null
+++ b/tests/test_wakatime_offlinequeue.py
@@ -0,0 +1,72 @@
+# -*- coding: utf-8 -*-
+
+
+from wakatime.main import execute
+from wakatime.offlinequeue import Queue
+from wakatime.packages import requests
+
+import os
+import time
+from wakatime.compat import u
+from wakatime.packages.requests.models import Response
+from . import utils
+
+
+class OfflineQueueTestCase(utils.TestCase):
+    patch_these = [
+        'wakatime.packages.requests.adapters.HTTPAdapter.send',
+        'wakatime.session_cache.SessionCache.save',
+        'wakatime.session_cache.SessionCache.delete',
+        ['wakatime.session_cache.SessionCache.get', requests.session],
+    ]
+
+    def test_heartbeat_saved_from_error_response(self):
+        response = Response()
+        response.status_code = 500
+        self.patched['wakatime.packages.requests.adapters.HTTPAdapter.send'].return_value = response
+
+        now = u(int(time.time()))
+        entity = 'tests/samples/twolinefile.txt'
+        config = 'tests/samples/sample.cfg'
+
+        args = ['--file', entity, '--alternate-project', 'xyz', '--config', config, '--time', now]
+        execute(args)
+
+        queue = Queue()
+        saved_heartbeat = queue.pop()
+        self.assertEquals(os.path.abspath(entity), saved_heartbeat['entity'])
+
+    def test_heartbeat_discarded_from_400_response(self):
+        response = Response()
+        response.status_code = 400
+        self.patched['wakatime.packages.requests.adapters.HTTPAdapter.send'].return_value = response
+
+        now = u(int(time.time()))
+        entity = 'tests/samples/twolinefile.txt'
+        config = 'tests/samples/sample.cfg'
+
+        args = ['--file', entity, '--alternate-project', 'xyz', '--config', config, '--time', now]
+        execute(args)
+
+        queue = Queue()
+        saved_heartbeat = queue.pop()
+        self.assertEquals(None, saved_heartbeat)
+
+    def test_offline_heartbeat_sent_after_success_response(self):
+        response = Response()
+        response.status_code = 500
+        self.patched['wakatime.packages.requests.adapters.HTTPAdapter.send'].return_value = response
+
+        now = u(int(time.time()))
+        entity = 'tests/samples/twolinefile.txt'
+        config = 'tests/samples/sample.cfg'
+
+        args = ['--file', entity, '--alternate-project', 'xyz', '--config', config, '--time', now]
+        execute(args)
+
+        response.status_code = 201
+        execute(args)
+
+        queue = Queue()
+        saved_heartbeat = queue.pop()
+        self.assertEquals(None, saved_heartbeat)
diff --git a/tests/utils.py b/tests/utils.py
index 9b8142e..862e3bd 100644
--- a/tests/utils.py
+++ b/tests/utils.py
@@ -3,9 +3,9 @@
 import logging
 
 try:
-    from mock import patch
+    import mock
 except ImportError:
-    from unittest.mock import patch
+    import unittest.mock as mock
 try:
     # Python 2.6
     import unittest2 as unittest
@@ -25,7 +25,7 @@ class TestCase(unittest.TestCase):
             for patch_this in self.patch_these:
                 namespace = patch_this[0] if isinstance(patch_this, (list, set)) else patch_this
 
-                patcher = patch(namespace)
+                patcher = mock.patch(namespace)
                 mocked = patcher.start()
                 self.patched[namespace] = mocked
 
@@ -36,4 +36,4 @@ class TestCase(unittest.TestCase):
                     mocked.return_value = retval
 
     def tearDown(self):
-        patch.stopall()
+        mock.patch.stopall()
diff --git a/wakatime/offlinequeue.py b/wakatime/offlinequeue.py
index 09efe41..8870e26 100644
--- a/wakatime/offlinequeue.py
+++ b/wakatime/offlinequeue.py
@@ -18,7 +18,7 @@ from time import sleep
 try:
     import sqlite3
     HAS_SQL = True
-except ImportError:
+except ImportError:  # pragma: nocover
     HAS_SQL = False
 
 from .compat import u
@@ -117,12 +117,12 @@ class Queue(object):
                         'plugin': row[8],
                     }
                 loop = False
-            except sqlite3.Error:
+            except sqlite3.Error:  # pragma: nocover
                 log.debug(traceback.format_exc())
                 sleep(wait)
                 tries -= 1
         try:
             conn.close()
-        except sqlite3.Error:
+        except sqlite3.Error:  # pragma: nocover
             log.debug(traceback.format_exc())
         return heartbeat