--- a/tests/test_cache.py
+++ b/tests/test_cache.py
@@ -302,7 +302,7 @@
         # adding 3-length permutations makes this test 10x slower but if you
         # are suspicious of a method caching you could uncomment this out:
         # attempts.extend([tuple(G) for G in itertools.permutations(flat, 3)])
-        skip = set()
+        skip = {"tofile", "dump"}
 
         # collect functions which mutate arrays but don't change our hash
         broken = []