Run terminal command before tests - Elixir

Question

I'm testing an S3 connection with fakeS3 and it works perfectly. The only downside is I have to run the fake S3 server every time before I run my tests or the S3 test will break obviously.

I want to figure out a way to run this command before my test run:

fakes3 -r ~/.s3bucket -p 4567

This will in theory start the Sinatra server so that the S3 test will pass but I don't need to start a separate server each time.

I've tried this and it didn't work for good reason:

MIX.exs

 test: ["ecto.create --quiet", "ecto.migrate", "fakes3 -r ~/.s3bucket -p 4567", "test"]

That doesn't work because it's not a mix task.

I'm also probably thinking of this the wrong way. How can I have the command run before my tests and is this the right way to think about this problem?

Answer 1

Just use ExUnit.Callbacks.setup_all/1:

def fakes3(_context) do
  System.cmd("fakes3", ~w|-r ~/.s3bucket -p 4567|)
  :ok
end

setup_all :fakes3

The above is to be put into the case you use to test S3.

---

BTW, this could be done with mix as well. It has run task that accepts either the script to run or an expression to eval as an argument:

test: [ 
  "ecto.create --quiet",
  "ecto.migrate",
  ~S[run -e "System.cmd(~s|fakes3|, ~w|-r ~/.s3bucket -p 4567|)"],
  "test"
]