diff --git a/PRESUBMIT.cfg b/PRESUBMIT.cfg
index 6dd237a..ff1ac81 100644
--- a/PRESUBMIT.cfg
+++ b/PRESUBMIT.cfg
@@ -4,6 +4,7 @@
 [Hook Scripts]
 cros lint = cros lint ${PRESUBMIT_FILES}
 pre-upload_unittest = ./pre-upload_unittest.py
+blocked_terms_unittest = ./blocked_terms_unittest.py
 
 [Hook Overrides]
 cros_license_check: true
diff --git a/blocked_terms.txt b/blocked_terms.txt
index 9d54a7d..220bd18 100644
--- a/blocked_terms.txt
+++ b/blocked_terms.txt
@@ -22,7 +22,7 @@
 \bhers\b
 man.?in.?the.?middle
 master
-mitm
+\bmitm(\b|\d)
 \bnative
 \bred.?line
 rtfm
diff --git a/blocked_terms_unittest.py b/blocked_terms_unittest.py
new file mode 100755
index 0000000..af80522
--- /dev/null
+++ b/blocked_terms_unittest.py
@@ -0,0 +1,113 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+# Copyright 2020 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""Unit tests for blocked_terms.txt and unblocked_terms.txt.
+
+   Implements unit tests for the blocked terms and unblocked terms
+   regex processed by pre-upload.py.
+"""
+
+from __future__ import print_function
+
+import os
+import sys
+
+
+# pylint: disable=W0212
+# We access private members of the pre_upload module all over the place.
+
+# Make sure we can find the chromite paths.
+sys.path.insert(0, os.path.join(os.path.dirname(os.path.realpath(__file__)),
+                                '..', '..'))
+
+# The sys.path monkey patching confuses the linter.
+# pylint: disable=wrong-import-position
+from chromite.lib import cros_test_lib
+from chromite.lib import osutils
+
+
+assert sys.version_info >= (3, 6), 'This module requires Python 3.6+'
+
+
+pre_upload = __import__('pre-upload')
+
+
+class CheckFilesTest(cros_test_lib.MockTestCase, cros_test_lib.TempDirTestCase):
+  """Tests for blocked and unblocked files."""
+
+  DIFF = 'diff'
+  MATCH = 'match'
+
+  def setUp(self):
+    pre_upload.CACHE.clear()
+
+    self.common_keywords = osutils.ReadFile(
+        os.path.join(pre_upload._get_hooks_dir(),
+                     pre_upload.BLOCKED_TERMS_FILE))
+
+    self.unblocked_keywords = osutils.ReadFile(
+        os.path.join(pre_upload._get_hooks_dir(),
+                     pre_upload.UNBLOCKED_TERMS_FILE))
+
+    self.PatchObject(pre_upload, '_get_affected_files',
+                     return_value=['x.ebuild'])
+    self.PatchObject(pre_upload, '_filter_files', return_value=['x.ebuild'])
+    self.rf_mock = self.PatchObject(osutils, 'ReadFile')
+    self.diff_mock = self.PatchObject(pre_upload, '_get_file_diff')
+    self.desc_mock = self.PatchObject(pre_upload, '_get_commit_desc')
+    self.project = pre_upload.Project(name='PROJECT', dir='./', remote=None)
+
+  def CheckKeyword(self, test):
+    # Test a particular keyword.
+    #
+    #  Args:
+    #   { DIFF:[list of values to test keyword against],
+    #     FAILURE:[list of expected failures] or None }
+    #
+    def __check_keyword(unblocked):
+      self.desc_mock.return_value = 'Commit message'
+      self.diff_mock.return_value = test[self.DIFF]
+      failures = pre_upload._check_keywords(self.project, 'COMMIT', ())
+      if test[self.MATCH] and not unblocked:
+        self.assertNotEqual(failures, [])
+        self.assertEqual('Found a blocked keyword in:', failures[0].msg)
+        self.assertEqual(test[self.MATCH], failures[0].items)
+      else:
+        self.assertEqual(failures, [])
+
+    self.rf_mock.side_effect = [self.common_keywords, str('')]
+    __check_keyword(unblocked=False)
+
+    self.rf_mock.side_effect = [self.common_keywords, self.unblocked_keywords]
+    __check_keyword(unblocked=True)
+
+  def test_mitm_keyword(self):
+    # pylint: disable=C0301
+
+    # { DIFF:[list of values to test keyword against],
+    #   FAILURE:[list of expected failures] or None },}
+    #
+    test_instance = {
+        self.DIFF:[(1, 'Line with blocked mitm '),
+                   (2, 'Line with blocked (mitm)'),
+                   (3, 'Line with blocked .mitm'),
+                   (4, 'Line with blocked MITM'),
+                   (5, 'Line with blocked mitm1'),
+                   (6, 'Line with unblocked (commitment)'),
+                   (7, 'Line with unblocked DailyLimitMins'),],
+        self.MATCH:[
+            'x.ebuild, line 1: Matched "mitm" with regex of "\\bmitm(\\b|\\d)"',
+            'x.ebuild, line 2: Matched "mitm" with regex of "\\bmitm(\\b|\\d)"',
+            'x.ebuild, line 3: Matched "mitm" with regex of "\\bmitm(\\b|\\d)"',
+            'x.ebuild, line 4: Matched "MITM" with regex of "\\bmitm(\\b|\\d)"',
+            'x.ebuild, line 5: Matched "mitm1" with regex of "\\bmitm(\\b|\\d)"'],
+    }
+
+    self.CheckKeyword(test_instance)
+
+
+if __name__ == '__main__':
+  cros_test_lib.main(module=__name__)
diff --git a/unblocked_terms.txt b/unblocked_terms.txt
index 6fc5f2b..feee3a6 100644
--- a/unblocked_terms.txt
+++ b/unblocked_terms.txt
@@ -33,7 +33,7 @@
 \bhers\b
 man.?in.?the.?middle
 master
-mitm
+\bmitm(\b|\d)
 \bnative
 \bred.?line
 rtfm