stevegee1
By default, `mix test` requires no command-line arg
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
cevado
the arg is whatever comes after the name, as a string, so the arg for mix test is 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
def run(_arg) do
...
end
you can find more details here:
https://hexdocs.pm/mix/Mix.Task.html
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