Ah, I misread the instrucions - I read the above ans 0->1->4->0 so a ring of 3!

It's showing a test case when it fails - eg [(0,[1]), (4,[0]), (1,[4])] ... 3 /= 1. Intuitively the solution is 3 and if I type the case into the eaxample tests it passes with 3. But I'm always getting a random failure with a spy ring of 3. Perhaps I'm missing something? Just to add, it could well be a problem with my solution - it took me a lot longer to solve than expected which makes it an interesting kata.

This is a nice kata. Could 'Attempt' return more information such as input and expected output for failed cases? Currently I get 'fails ater n tests and m shrinks' and an input. When I manually type the input and deduced answer into the examples it always passes so I don't know where/why it's failing. Cheers

The description uses 0.02 for 2 percent, the first test case uses 5.0 for 5 percent. Otherwise a good kata.

A good idea for a kata. Just a couple of minor points:

1. Arguments/variables generally start with lower case letters, upper case is convetionally used for class names.
2. Either produce a test case that satisfies the kata system or none at all. ie, move the test case code into the description.
   Nice one ... I think I'm going to have another go :)

Great kata, thanks.

How small is the probability of failing the mean and variance tests? Could the tests be run enough times per submission to sufficiently reduce the probabability of false negatives and make the disclaimer redundant?