lib/basic_signup_whitelist.ex

@@ -18,12 +18,8 @@ defmodule BasicSignupWhitelist do
 
   ## Examples
 
-      iex> System.delete_env("SIGNUP_ALLOWED_EMAILS")
       iex> BasicSignupWhitelist.mail_whitelisted("joe@example.com")
       false
-      iex> System.put_env("SIGNUP_ALLOWED_EMAILS","*")
-      iex> BasicSignupWhitelist.mail_whitelisted("joe@example.com")
-      true
 
   """
   def mail_whitelisted(email) do

test/basic_signup_whitelist_test.exs

@@ -1,16 +1,21 @@
 defmodule BasicSignupWhitelistTest do
-  use ExUnit.Case, async: false
+  use ExUnit.Case
   doctest BasicSignupWhitelist
 
   defp allow_signups_for(whitelist) do
     System.put_env("SIGNUP_ALLOWED_EMAILS", whitelist)
   end
 
-  describe "setup in describe block" do
   setup do
+    # Save original env var
+    original_env = System.get_env("SIGNUP_ALLOWED_EMAILS")
+
     on_exit(fn ->
-        # resetting values did not work, so 'just' set it to the effect without this module configured.
-        System.put_env("SIGNUP_ALLOWED_EMAILS", "*")
+      # Restore original env var after each test
+      case original_env do
+        nil -> System.delete_env("SIGNUP_ALLOWED_EMAILS")
+        value -> System.put_env("SIGNUP_ALLOWED_EMAILS", value)
+      end
     end)
 
     :ok
@@ -25,5 +30,4 @@ defmodule BasicSignupWhitelistTest do
     allow_signups_for("*")
     assert BasicSignupWhitelist.mail_whitelisted("joe@example.com")
   end
-  end
 end