basic_signup_allowlist/test/basic_signup_allowlist_test.exs

defmodule BasicSignupAllowlistTest do
  use ExUnit.Case, async: false
  doctest BasicSignupAllowlist

  defp allow_signups_for(allowlist) do
    System.put_env(BasicSignupAllowlist.signup_allowlist_emails(), allowlist)
  end

  describe "setup in describe block" do
    setup do
      on_exit(fn ->
        # resetting values did not work, so 'just' set it to the effect without this module configured.
        System.put_env(BasicSignupAllowlist.signup_allowlist_emails(), "*")
      end)

      :ok
    end

    test "When not set, not allowlisted" do
      System.delete_env(BasicSignupAllowlist.signup_allowlist_emails())
      refute BasicSignupAllowlist.mail_allowlisted("joe@example.com")
    end

    test "When set to star, allowlisted" do
      allow_signups_for("*")
      assert BasicSignupAllowlist.mail_allowlisted("joe@example.com")
    end
  end
end