I corrected the Example Test Case for Elixir.

If CW comes back to the older version (OTP 18?), the changes will have to be made again... in the other way. I suppose that the "random/rand replace" comes from the change OTP 18 --> OTP 19.

There were Elixir or OTP changes at CW. Everything was fine when I publish this kata.
I have just replaced randomby rand but now I get

=INFO REPORT==== ....
application: logger
exited: {{shutdown,{failed_to_start_child,'Elixir.GenEvent',undef}},
{'Elixir.Logger.App',start,[normal,[]]}}
type: temporary

but that doesn't harm the tests so you could give it a new try. I have reported the INFO REPORT as a "bug" on github;
https://github.com/Codewars/codewars.com/issues/428.

I fixed the 'random' error.

If you have another issue, please make it in a separate comment/thread.

Looking at the code I see no issue, but I don't actually know Elixir.

It clearly says assert make_negative(42) == -42 in the test case.
Where are you seeing this?

The error I don't know anything about.

They are not broken... See the bug report I have done: https://github.com/Codewars/codewars.com/issues/428. I will try to make things fixed, at least temporarily.
Maybe you could see something like that:

=INFO REPORT==== .... ===
application: logger
exited: {{shutdown,{failed_to_start_child,'Elixir.GenEvent',undef}},
{'Elixir.Logger.App',start,[normal,[]]}}
type: temporary

but that don't break the tests .. if your code is correct:-)