Tester for url increment/decrement with zeroes

qutebrowser/utils/urlutils.py

@@ -528,7 +528,7 @@ def incdec_number(url, incdec, segments=None):
             if len(number) < len(str(val)):
                 zeroes = zeroes[1:]
             if len(number) > len(str(val)):
-                zeroes = ''.join([zeroes,'0'])
+                zeroes = ''.join([zeroes, '0'])
 
         new_value = ''.join([pre, zeroes, str(val), post])
         setter(new_value)

tests/unit/utils/test_urlutils.py

@@ -586,6 +586,34 @@ class TestIncDecNumber:
             base_url, incdec, segments={'host', 'path', 'query', 'anchor'})
         assert new_url == expected_url
 
+    @pytest.mark.parametrize('number, expected', [
+        ('01', '02'),
+        ('09', '10'),
+        ('009', '010')
+        ])
+    def test_increment_leading_zeroes(self, number, expected):
+        """Test incdec_number with leading zeroes."""
+        url = 'http://example.com/{}'
+        base_url = QUrl(url.format(number))
+        expected_url = QUrl(url.format(expected))
+        new_url = urlutils.incdec_number(
+                base_url, 'increment', segments={'path'})
+        assert new_url == expected_url
+
+    @pytest.mark.parametrize('number, expected', [
+        ('02', '01'),
+        ('10', '9'),
+        ('010', '009')
+        ])
+    def test_decrement_leading_zeroes(self, number, expected):
+        """Test incdec_number with leading zeroes."""
+        url = 'http://example.com/{}'
+        base_url = QUrl(url.format(number))
+        expected_url = QUrl(url.format(expected))
+        new_url = urlutils.incdec_number(
+                base_url, 'increment', segments={'path'})
+        assert new_url == expected_url
+
     @pytest.mark.parametrize('url, segments, expected', [
         ('http://ex4mple.com/test_4?page=3#anchor2', {'host'},
          'http://ex5mple.com/test_4?page=3#anchor2'),