diff --git a/tests/test_heartbeat.py b/tests/test_heartbeat.py
new file mode 100644
index 0000000..d7b0628
--- /dev/null
+++ b/tests/test_heartbeat.py
@@ -0,0 +1,110 @@
+# -*- coding: utf-8 -*-
+
+
+from wakatime.heartbeat import Heartbeat
+
+import os
+import logging
+from testfixtures import log_capture
+from .utils import TestCase
+
+
+class HeartbeatTestCase(TestCase):
+
+    @log_capture()
+    def test_sanitize_removes_sensitive_data(self, logs):
+        logging.disable(logging.NOTSET)
+
+        class Args(object):
+            exclude = []
+            hidefilenames = ['.*']
+            include = []
+            plugin = None
+
+        data = {
+            'entity': os.path.realpath('tests/samples/codefiles/python.py'),
+            'type': 'file',
+            'project': 'aproject',
+            'branch': 'abranch',
+        }
+        heartbeat = Heartbeat(data, Args(), None)
+        sanitized = heartbeat.sanitize()
+        self.assertEquals('HIDDEN.py', sanitized.entity)
+        sensitive = [
+            'branch',
+            'dependencies',
+            'lines',
+            'lineno',
+            'cursorpos',
+        ]
+        for item in sensitive:
+            self.assertIsNone(getattr(sanitized, item))
+
+        self.assertNothingPrinted()
+        self.assertNothingLogged(logs)
+
+    @log_capture()
+    def test_sanitize_does_nothing_when_hidefilenames_false(self, logs):
+        logging.disable(logging.NOTSET)
+
+        class Args(object):
+            exclude = []
+            hidefilenames = []
+            include = []
+            plugin = None
+
+        data = {
+            'entity': os.path.realpath('tests/samples/codefiles/python.py'),
+            'type': 'file',
+            'project': 'aproject',
+            'branch': 'abranch',
+        }
+        heartbeat = Heartbeat(data, Args(), None)
+        heartbeat.branch = data['branch']
+        sanitized = heartbeat.sanitize()
+        self.assertEquals(data['branch'], sanitized.branch)
+
+        self.assertNothingPrinted()
+        self.assertNothingLogged(logs)
+
+    @log_capture()
+    def test_sanitize_does_nothing_when_missing_entity(self, logs):
+        logging.disable(logging.NOTSET)
+
+        class Args(object):
+            hidefilenames = ['.*']
+            plugin = None
+
+        branch = 'abc123'
+        data = {
+            'entity': None,
+            'type': 'file',
+            'branch': branch,
+        }
+        heartbeat = Heartbeat(data, Args(), None, _clone=True)
+        sanitized = heartbeat.sanitize()
+        self.assertEquals(branch, sanitized.branch)
+
+        self.assertNothingPrinted()
+        self.assertNothingLogged(logs)
+
+    @log_capture()
+    def test_sanitize_does_nothing_when_type_not_file(self, logs):
+        logging.disable(logging.NOTSET)
+
+        class Args(object):
+            hidefilenames = ['.*']
+            plugin = None
+
+        branch = 'abc123'
+        data = {
+            'entity': 'not.a.file',
+            'type': 'app',
+            'branch': branch,
+        }
+        heartbeat = Heartbeat(data, Args(), None, _clone=True)
+        sanitized = heartbeat.sanitize()
+        self.assertEquals(branch, sanitized.branch)
+
+        self.assertNothingPrinted()
+        self.assertNothingLogged(logs)
diff --git a/wakatime/heartbeat.py b/wakatime/heartbeat.py
index c60d188..3898150 100644
--- a/wakatime/heartbeat.py
+++ b/wakatime/heartbeat.py
@@ -62,7 +62,7 @@ class Heartbeat(object):
                 return
             if self.type == 'file':
                 self.entity = format_file_path(self.entity)
-            if self.type == 'file' and not os.path.isfile(self.entity):
+            if self.type == 'file' and (not self.entity or not os.path.isfile(self.entity)):
                 self.skip = u('File does not exist; ignoring this heartbeat.')
                 return