Great Kata, but Python version is much more difficult than 8 kyu. I understand rules and ranks cannot be change, but what would make this kata much simpler and get it to 8 kyu in Python would be simpler test case, for example: removing all test cases with range iterators and only keeping list and string.

Thanks to the author for putting this Kata. The Kata is rated less, but it has a good concept behind it. Try not to scan the whole sequence.

Some languages don't have random tests.

Why the F... iterators are tested in the python version?

1. nothing is told about that in the description
2. that doesn't fit an 8 kyu challenge.

I think the point of this kata was that solutions should work with any type of sequences that exists in a language (although the current rank of 8 kyu doesn't match this task), so the Elixir version should have tests with infinite streams.

Could use some random test cases:

  it "should work for random examples" $ do
    property $ \x xs ->
      next x xs `shouldBe solution x (xs :: String)
where solution x xs = -- a valid solution

just some idea, maybe we could test if the solution submitted eval the sequence eagerly?
thx for the kata!