diff --git a/cmeutils/tests/test_visualize.py b/cmeutils/tests/test_visualize.py
index 3b96adf..9022c35 100644
--- a/cmeutils/tests/test_visualize.py
+++ b/cmeutils/tests/test_visualize.py
@@ -80,6 +80,7 @@ def set_set_colors(self, p3ht_fresnel):
         colors = np.zeros_like(p3ht_fresnel.positions)
         colors[:] = np.array([0.5, 0.5, 0.5])
         p3ht_fresnel.colors = colors
+        assert all(np.array_equal(colors, p3ht_fresnel.colors))
 
     def test_unwrap_positions(self, p3ht_fresnel):
         assert p3ht_fresnel.unwrap_positions is False