diff --git a/backend/tests/services/test_cadastre_bulk.py b/backend/tests/services/test_cadastre_bulk.py
index 9cd3ddf7..f33513a7 100644
--- a/backend/tests/services/test_cadastre_bulk.py
+++ b/backend/tests/services/test_cadastre_bulk.py
@@ -18,7 +18,10 @@ from app.services.cadastre.bulk_harvest import (
     _safe_numeric,
     upsert_features,
 )
-from app.services.cadastre.grid_geometry import generate_grid_click_points
+from app.services.cadastre.grid_geometry import (
+    generate_grid_click_points,
+    quarter_bbox_3857,
+)
 
 # ── Фикстуры ─────────────────────────────────────────────────────────────────
 
@@ -195,6 +198,52 @@ def test_generate_grid_click_points_custom_grid() -> None:
     assert cell_bbox[3] - cell_bbox[1] == pytest.approx(200.0)
 
 
+# ── quarter_bbox_3857 sanity check ───────────────────────────────────────────
+
+
+def _mock_db_with_bbox(
+    xmin: float | None, ymin: float | None, xmax: float | None, ymax: float | None
+) -> MagicMock:
+    """Mock SQLAlchemy session.execute().mappings().first() возвращает заданный bbox."""
+    mock_db = MagicMock()
+    row = None if xmin is None else {"xmin": xmin, "ymin": ymin, "xmax": xmax, "ymax": ymax}
+    mock_db.execute.return_value.mappings.return_value.first.return_value = row
+    return mock_db
+
+
+def test_quarter_bbox_3857_healthy_geom() -> None:
+    """Real ЕКБ-квартал ~750м — должен пройти sanity check."""
+    db = _mock_db_with_bbox(6735845.0, 8329000.0, 6736595.0, 8329750.0)
+    bbox = quarter_bbox_3857(db, "66:41:0303161")
+    assert bbox is not None
+    assert bbox == (6735845.0, 8329000.0, 6736595.0, 8329750.0)
+
+
+def test_quarter_bbox_3857_skips_broken_micro_geom() -> None:
+    """width < 100m — broken micro-precision geom (72% rows в cad_quarters_geom)."""
+    # width=60.7m — реальный broken quarter 66:41:0101005 после ST_Transform
+    db = _mock_db_with_bbox(60.0, 60.0, 120.7, 120.7)
+    assert quarter_bbox_3857(db, "66:41:0101005") is None
+
+
+def test_quarter_bbox_3857_skips_oversized_geom() -> None:
+    """width > 10000m — broken/regional geom (не городской квартал)."""
+    db = _mock_db_with_bbox(0.0, 0.0, 15000.0, 15000.0)
+    assert quarter_bbox_3857(db, "66:41:9999999") is None
+
+
+def test_quarter_bbox_3857_skips_zero_height() -> None:
+    """height < 100m — симметрия по другой оси."""
+    db = _mock_db_with_bbox(0.0, 0.0, 500.0, 50.0)
+    assert quarter_bbox_3857(db, "66:41:0000001") is None
+
+
+def test_quarter_bbox_3857_returns_none_when_quarter_missing() -> None:
+    """Квартал не найден в cad_quarters_geom → None (xmin IS NULL)."""
+    db = _mock_db_with_bbox(None, None, None, None)
+    assert quarter_bbox_3857(db, "66:99:0000000") is None
+
+
 # ── upsert_features routing ──────────────────────────────────────────────────