Whitelist two addresses

Intermediate steps not committed - addresses_as_list, because long stack
trace in output. turned out 'nil' case needs to be explicit now. I
prefer the small functions though instead of whole implementation in
case statement.

test/fun_core/basic_signup_whitelist_test.exs

@@ -1,10 +1,37 @@
 defmodule FunCore.BasicSignupWhitelistTest do
   use ExUnit.Case
 
-  def mail_whitelisted_fun(signups_allowed, email_received) do
-    signups_allowed == email_received
+  defp normalize(email) do
+    email |> String.trim()
   end
 
+  defp addresses_as_list(addresses_str) do
+    addresses_str
+    |> String.split(",")
+    |> Enum.map(&normalize/1)
+  end
+
+  def mail_whitelisted_fun(signups_allowed, email_received) do
+    case signups_allowed do
+      nil -> false
+      "*" -> true
+      list_str -> email_received in addresses_as_list(list_str)
+    end
+  end
+
+  test "addresses_as_list" do
+    assert addresses_as_list("joe@example.com, jane@example.com") == [
+             "joe@example.com",
+             "jane@example.com"
+           ]
+  end
+
+  test "jane in list" do
+    lst = addresses_as_list("joe@example.com, jane@example.com")
+    assert "jane@example.com" in lst
+  end
+
+  # test for normalize
   describe "Not whitelisted when allowed list is" do
     test "not set" do
       refute(mail_whitelisted_fun(nil, "joe@example.com"))
@@ -15,7 +42,13 @@ defmodule FunCore.BasicSignupWhitelistTest do
     end
   end
 
-  test "When set and mach, then whitelisted" do
-    assert(mail_whitelisted_fun("joe@example.com", "joe@example.com"))
+  describe "Whitelisted when" do
+    test "*" do
+      assert(mail_whitelisted_fun("*", "jane@example.com"))
+    end
+
+    test "Multiple set and one match" do
+      assert(mail_whitelisted_fun("joe@example.com, jane@example.com", "jane@example.com"))
+    end
   end
 end