Really stupid mistake on my part - thank you!

Check your curly brackets.

When I submit my solution in Javascript, I get this message:

'Response received but no data was written to STDOUT or STDERR.'

Clearly I've missed something, but it's a most unhelpful message...

Jesus Christ, this was so annoying. So many random Cases, always had 1-10 out of 100 Test cases causing errors.

Random tests, Javascript:

Testing for an array of length = 7887
Wanted term (k) : 6949

Although the array has length 7887, this random test only has 6561 distinct values in the array. So it should output 'No way.'

I get this failure message:
'expected 'No way' to equal 'Valid entries: 'max' or 'min''

It's possible I've messed up somewhere, but this might be a mistake in the random tests - the value of k should be checked before the correctness of the string.

You're not just creating a model with this one - you are also choosing a model, and then testing data against it. Which makes it a bit more complex.

In Java, returning this as a string seems odd. It would be much more natural to return an ArrayList.