stricter test

tests/test_h3.py

@@ -496,14 +496,19 @@ def cells_at_res(res):
         for parent in cells:
             yield from h3.cell_to_children(parent, res)
 
-    def roundtrip(children, res_parent):
-        for c in children:
-            parent = h3.cell_to_parent(c, res_parent)
-            pos = h3.cell_to_child_pos(res_parent, c)
-            yield h3.child_pos_to_cell(parent, res_child, pos)
-
-    for res_parent in [0, 1]:
-        for res_child in [0, 1, 2, 3]:
-            if res_parent <= res_child:
-                children = set(cells_at_res(res_child))
-                assert set(roundtrip(children, res_parent)) == children
+    def roundtrip(child, res_parent):
+        res_child = h3.get_resolution(child)
+        parent = h3.cell_to_parent(child, res_parent)
+        pos = h3.cell_to_child_pos(res_parent, child)
+        return h3.child_pos_to_cell(parent, res_child, pos)
+
+    res_pairs = [
+        (res_parent, res_child)
+        for res_parent in [0, 1]
+        for res_child in [0, 1, 2, 3]
+        if res_parent <= res_child
+    ]
+
+    for res_parent, res_child in res_pairs:
+        for child in cells_at_res(res_child):
+            assert child == roundtrip(child, res_parent)