diff --git a/tests/test_process_diff.py b/tests/test_process_diff.py
new file mode 100644
index 0000000..8fa1dc1
--- /dev/null
+++ b/tests/test_process_diff.py
@@ -0,0 +1,59 @@
+import json
+import os
+import unittest
+import tempfile
+import subprocess
+import io
+
+from TodoParser import TodoParser
+from main import process_diff
+
+
+class IssueUrlInsertionTest(unittest.TestCase):
+    orig_cwd = None
+    tempdir = None
+    diff_file = None
+    parser = None
+
+    def setUp(self):
+        # get current working directory
+        self.orig_cwd = os.getcwd()
+
+        # Create temporary directory to hold simulated filesystem.
+        self.tempdir = tempfile.TemporaryDirectory()
+
+        # run patch against the diff file to generate the simulated filesystem
+        subprocess.run(['patch', '-d', self.tempdir.name,
+                        '-i', f'{os.getcwd()}/tests/test_new.diff'],
+                        stdout=subprocess.DEVNULL,
+                        stderr=subprocess.DEVNULL,
+                        check=True)
+
+        self.diff_file = open('tests/test_new.diff', 'r')
+        self.parser = TodoParser()
+        with open('syntax.json', 'r') as syntax_json:
+            self.parser.syntax_dict = json.load(syntax_json)
+
+        # change to the simulated filesystem directory
+        os.chdir(self.tempdir.name)
+
+    # this test can take a while and, as far as TodoParser is concerned,
+    # redundant with the tests of test_todo_parser, so enable the means
+    # to skip it if desired
+    @unittest.skipIf(os.getenv('SKIP_PROCESS_DIFF_TEST', 'false') == 'true',
+                     "Skipping because 'SKIP_PROCESS_DIFF_TEST' is 'true'")
+    def test_url_insertion(self):
+        # create object to hold output
+        output = io.StringIO()
+        # process the diffs
+        process_diff(diff=self.diff_file, insert_issue_urls=True, parser=self.parser, output=output)
+        # make sure the number of issue URL comments inserted is as expected
+        self.assertEqual(output.getvalue().count('Issue created: #None @ N/A'), 82)
+
+    def tearDown(self):
+        # return to original working directory to ensure we don't mess up other tests
+        os.chdir(self.orig_cwd)
+
+        # explicitly cleanup to avoid warning being printed about implicit cleanup
+        self.tempdir.cleanup()
+        self.tempdir = None