Add checkpoint logic and tests

tests/test_listing.py

@@ -11,6 +11,7 @@ class _FakePage:
     def __init__(self, counts: dict[str, int]) -> None:
         self._counts = counts
         self._evaluate_result = False
+        self._evaluate_values: list[object] = []
 
     class _Locator:
         def __init__(self, count_value: int) -> None:
@@ -23,6 +24,8 @@ class _FakePage:
         return _FakePage._Locator(self._counts.get(selector, 0))
 
     def evaluate(self, _script: str):
+        if self._evaluate_values:
+            return self._evaluate_values.pop(0)
         return self._evaluate_result
 
 
@@ -40,6 +43,11 @@ class TestListingUnit(unittest.TestCase):
         page._evaluate_result = True
         self.assertTrue(ListingCollector._has_next_page(page))
 
+    def test_get_current_page_number_from_text_counter(self) -> None:
+        page = _FakePage({})
+        page._evaluate_values = [5]
+        self.assertEqual(ListingCollector._get_current_page_number(page), 5)
+
     def test_extract_vehicle_links_from_html_finds_detail_urls(self) -> None:
         collector = ListingCollector(Settings(), HumanPacer(Settings()))
         html = """