Had the same problem. But read exactly:
Every item can have a quality above 50.
It is only said that it won't increase further if it has reached 50 or higher.

Yes. Maybe my for my next kata published, I may actually get on the leaderboard on authored katas.

warning: sounds good, yes (actually, expecting outputs smaller than the input is just an error in the reasonning, yes)

2dan: 5.0% left. Hence... Still some months to go, I guess x) (maybe still in 2020. 'Will mostly depend on my motivation. Which is pretty low these days... :/ )

Also, added message that shows n and k.

@Blind4Basics
Some solutions rely on the highest n can be, so maybe not. Should I just warn users that the result may be way larger than 1e6.
Btw, how far are you from 2 dan, I'm just curious;-)

The numbers tested are less than 10^6. However, the result may be larger

@tonylicoding: are those restrictions really needed? maybe just remove them, warning the user that huge numbers will be tested too? (you could add one or two of this kind of sample tests to make it clear)?

(Python)

In kata descrition there is a note:
1<n<10^6
1<k<10

I have some failing tests and this is the output of one of them:
"81514610699888 should equal 5094663168743"
Those numbers are much bigger than 10^6
Log output should be more descriptive like: for n=some value (k=val2) should equal: val3

I think there's still problem with this kata.
In the description it's said:
Just for extra clarification, an item can never have its quality increase above 50, however "Sulfuras" is a legendary item and as such its quality is 80 and it never alters.

And here's a part of log from random tests:
Starting items in the store are {Very Aged Brie, 2, 60}, {Potion of Weak Love, 6, 58} and 5 days passed
Checking item 1: Very Aged Brie
Test Passed
Not the expected quality value: 50 should equal 60

According to the description only sulfuras can have quality >50. Besides - 5 days passed condition and quality raised by 2 each day.. where it is said?
Please, verify requirements vs tests.

Python