stevegee1
From my understanding, writing a custom Mix task requires this implementation:
def run(arg) do
...
end
Without this above implementation, Mix raises:
** (Mix) The task "xyz" does not export run/1
So studying, mix test module, it implemented the same function but I could safely run mix test in my project without command-line option. Why is that?
Thanks! 
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NobbZ
It implements
run/1and then parses the options, with an option parser that knows what to do whenargsis empty.cevado
the arg is whatever comes after the name, as a string, so the arg for
mix testis just""an empty string. the arity of the function doesn’t define if you have args or not, it’s a behaviour the expected arity is always 1 no matter what.what you can do is just implement it as
you can find more details here:
stevegee1
Thanks for the clarification! @cevado @NobbZ
It makes so much sense now!