Fix assertion message in the test.

Author: tpprytula

tests/test_nd_volume.py

@@ -32,7 +32,9 @@ def test_nd_cube(dim: int, make_cube: Callable[[int], np.ndarray]) -> None:
     assert isinstance(edges, list)
     assert len(vertices) >= 1, "There should be at least one vertex in the graph"
     assert isinstance(vertices[0], tuple), "The first vertex should be a tuple"
-    assert len(vertices[0]) == dim, "The first vertex should have n coordinates"
+    assert (
+        len(vertices[0]) == dim
+    ), "The first vertex should have as many coordinates as dim"
 
     assert set(vertices[0]).issubset(
         {24, 25}