How to hide logs in some tests but not in others?

Question

Background

I have library that logs messages depending on the value of disable_logging:

unless Application.get(:my_app, :disable_logging, false), do:
  Logger.info("Hello World!")

Depending on MIX_ENV I have a config for each setup:

#test.config
use Mix.Config
config :my_app, disable_logging: true

Problem

The issue here is that I don't want log messages all over my test results. So, naturally, I could set the disable_logging to true and be done with it.

However, if I do it, I can't test whether or not the Logger is being called and if it's being called with the correct values:

• https://hexdocs.pm/ex_unit/ExUnit.CaptureLog.html

Question

So, given this I have some questions:

1. Is there a way to activate logs but without outputting them to the terminal when I am running tests?
2. Is there a way to only activate logs for some tests in my test suite?

Answer 1

Declare ExUnit.setup/1 with a mandatory ExUnit.on_exit/2 to set the environment variable with Application.put_env/4.

setup do
  Application.put_env(:my_app, :disable_logging, false)

  on_exit fn ->
    Application.put_env(:my_app, :disable_logging, true)
  end

  :ok
end

I did not test it, but it should work.