And that is why using var is generally considered as a bad practice...

It's difficult understanding some katas like this one, challenging.

Random tests should also generate invalid cases (at least 30-50% of the time) and not just rely on fixed and sample tests (presumably all languages)

Missing fixed, sample and random tests for cases below:

• n = true / false

• n is a floating-point number (1.23)

python new test framework is required. updated in this fork

python new test framework is required. updated in this fork

same solution

Oh I see now. I was confused because I thought you were checking for duplicates in the set, which wouldn't make sense. Thanks for your help!

How to fix this. "There are not only hex-chars in argument." I use regexp for checking the arg and i can find the problem

for JavaScript doesn't work for any response of the function except for throwing errors for test case:
Test.expectError("Incorrect hex-string length", function(){getReversedColor("1234567")});

returning false, returning nothing, NaN, undefined, 0 etc. still causes test error.
Throwing errors is not considered a common practice in JavaScript, so I strongly suggest either change the ourcome expectation for invalid inputs, or mention this in the description clearly.
As for now description only includes Java and Haskell:
"If the entered string is incorrect: length is 7+, has non-hexadecimal characters or non-string type, then the Error(IllegalArgumentException - Java) should be raised/thrown or Nothing should be returned in Haskell."

It's how percent decrease works. Increase in 0.82 times is equal to decrease in 0.18 times.