CODEWITHSUNDEEP
unit-testingloggingelixirex-unit
Flame_Phoenix
Flame_Phoenix

Reputation: 17574

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

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:

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?

Upvotes: 0

Views: 389

Answers (2)

Sheharyar
Sheharyar

Reputation: 75760

Why not keep using ExUnit.CaptureLog to suppress the logs and just discard the result?

If you have a large number of tests that log to console and don't want to do that for all of them, you can create a custom ExUnit tag, combined with @Aleksei's answer, that does it for you.

In your ExUnit.Case template, add this:

setup tags do
  if tags[:disable_logger] do
    Application.put_env(:my_app, :disable_logging, false)

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

  :ok
end

Now you can just specify the tag for the tests you want logging disabled for:

@tag disable_logger: true
test "something happens" do
  # ...
end

Note: You will encounter issues with this if you run your tests asynchronously

Upvotes: 1

Aleksei Matiushkin
Aleksei Matiushkin

Reputation: 121000

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.

Upvotes: 1

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