Add one more boundary box test.

roentgen/tile.py

@@ -188,12 +188,9 @@ class Tile:
             self.x + 1, self.y + 1, self.scale
         ).get_coordinates()
 
-        lat_2 = point_1[0]
-        lon_1 = point_1[1]
-        lat_1 = point_2[0]
-        lon_2 = point_2[1]
-
-        return BoundaryBox(lon_1, lat_1, lon_2, lat_2).round()
+        return BoundaryBox(
+            point_1[1], point_2[0], point_2[1], point_1[0]
+        ).round()
 
     def load_map(self, cache_path: Path) -> Map:
         """

test/test_boundary_box.py

@@ -7,7 +7,13 @@ __author__ = "Sergey Vartanov"
 __email__ = "me@enzet.ru"
 
 
-def test_extend() -> None:
+def test_round_zero_coordinates() -> None:
+    box: BoundaryBox = BoundaryBox(0, 0, 0, 0).round()
+
+    assert box.get_format() == "-0.001,-0.001,0.001,0.001"
+
+
+def test_round_coordinates() -> None:
     box: BoundaryBox = BoundaryBox(
         10.067596435546875,
         46.094186149226466,