adds failing test with overlapping incremental cursor values.

tests/extract/test_incremental.py

@@ -669,6 +669,47 @@ def some_data(
     assert s["last_value"] == 2
 
 
+@pytest.mark.parametrize("item_type", ALL_TEST_DATA_ITEM_FORMATS)
+def test_cursor_path_none_does_not_include_overlapping_records(
+    item_type: TestDataItemFormat,
+) -> None:
+    @dlt.resource
+    def some_data(
+        invocation: int,
+        created_at=dlt.sources.incremental("created_at", on_cursor_value_missing="include"),
+    ):
+        if invocation == 1:
+            yield data_to_item_format(
+                item_type,
+                [
+                    {"id": 1, "created_at": None},
+                    {"id": 2, "created_at": 1},
+                    {"id": 3, "created_at": 2},
+                ],
+            )
+        elif invocation == 2:
+            yield data_to_item_format(
+                item_type,
+                [
+                    {"id": 4, "created_at": 1},
+                    {"id": 5, "created_at": None},
+                    {"id": 6, "created_at": 3},
+                ],
+            )
+
+    p = dlt.pipeline(pipeline_name=uniq_id())
+    p.run(some_data(1), destination="duckdb")
+    p.run(some_data(2), destination="duckdb")
+
+    assert_query_data(p, "select id from some_data order by id", [1, 2, 3, 5, 6])
+    assert_query_data(p, "select created_at from some_data order by created_at", [1, 2, 3, None, None])
+
+    s = p.state["sources"][p.default_schema_name]["resources"]["some_data"]["incremental"][
+        "created_at"
+    ]
+    assert s["last_value"] == 3
+
+
 @pytest.mark.parametrize("item_type", ALL_TEST_DATA_ITEM_FORMATS)
 def test_cursor_path_none_includes_records_and_updates_incremental_cursor_2(
     item_type: TestDataItemFormat,