Run doctests in unittests...

...and fix one wrong doctest

huey_monitor/humanize.py

@@ -49,8 +49,8 @@ def percentage(num, total) -> str | None:
     '25%'
     >>> percentage(33.333, 100)
     '33%'
-    >>> percentage(123, 0)
-    None
+    >>> percentage(123, 0) is None
+    True
     """
     if not total:
         return None

huey_monitor_project/tests/test_doctest.py

@@ -0,0 +1,17 @@
+from bx_py_utils.test_utils.unittest_utils import BaseDocTests, DocTestResults
+
+import huey_monitor
+import huey_monitor_project
+
+
+class DocTests(BaseDocTests):
+    def test_doctests(self):
+        results: DocTestResults = self.run_doctests(
+            modules=(
+                huey_monitor,
+                huey_monitor_project,
+            )
+        )
+        self.assertGreaterEqual(results.passed, 25)
+        self.assertEqual(results.skipped, 0)
+        self.assertLessEqual(results.failed, 0)