seems as usual,nothing changed

Good kata,bad test.It was the worst test cases I had seen.

I can't see it...but the kata has been solved. A reply marked as a spoiler should be visiable for questioner.I will advise this to CodeWars.
Thank you!

Hey Surtich.
I can't see your reply because it's marked as a spoiler...
edit: it's ok now. thanks i'll look at this

I got the same problems with igorredchuk:

set/del-> redo tests

It should have thrown an exception. After set call, there is nothing to redo
Test Passed: Value == {"x":5}
one redo call - Expected: {"x":5,"y":66}, instead got: {"x":5,"y":6}

It's really hard for me to investigate the problem. What did I miss？I would appreciate a hint. Thanks!

Have you solved it?I've met the same problem.

Ah thank you. I did see that first time around, but your comment made me do a bit more googling :).

The hint's at end of description (in small typo):
Hint: in this kata you'll try to define properties of an object

MDN may help also.

It's so hard for me.I solved it by stackoverflow.Good Kata!