Thanks for making this Kata!
I found the instructions to "add one" a bit misleading for this example:

[1,0,0,0]
invert: [0,1,1,1] (= 7)
add 1: [1,1,0,0,0] (= 8)

Maybe include this example and say:

[1,0,0,0]
invert: [0,1,1,1] (= 7)
add 1 treating the number as binary: [1,0,0,0] (= 8 in binary, = -8 in 2's complement).

(I'm new to 2's complement, so maybe it's only confusing for people not familiar with it)

@FArekkusu: see the issue above, plz

this sentence in the description makes close to no sense according to the task:

However, the arrays can have varying lengths, not just limited to 4.

It should be replaced with something like (hopefully (edit: it does) this will match JS and C# too...?)

The output array must have the same length than the input array

and at least one fixed tests with a different length should be added (both to test cases and example tests parts)

check the thread just below this

thank you @rowcased. Iam done. What was fixed?

The reference solution has been fixed, so, refresh the page, reset the trainer and try again.

Nice done, thank you @FArekkusu :) (even if this invalidate previous solutions ;P)

Submitted my own solution. All works now.

I have fixed the reference solution. Please, reset the trainer and try again.

@stɛffan153: actually JS random tests produce input of length < 4 and expect result of length 4 :(

I'm totally agree with you... that should be stated in the kata description and better if minimum length 4 is required, expected result of input such as [ 0, 1, 0 ] should be [ 1, 1, 1, 0 ] but not [ 0, 1, 1, 0 ] as it is actually ^^

It doesn't need to be of length 4. It needs to be of whatever length that the array passed in was.

[0,0,1,0] = 2 in base 10

[1,1,0,1] <- Flip the bits

Add 1

[1,1,1,0] = -2

i dont understand this

If you like, you can post your code with proper code markdown, (and don't forget to use the spoiler tag). I'll take a look and debug what I can/should for you.