test(elixir): approval test for 30 days

elixir/test/gilded_rose_test.exs

@@ -1,6 +1,13 @@
 defmodule GildedRoseTest do
   use ExUnit.Case
 
+  import ExUnit.CaptureIO
+
+  test "Approval test 30 days" do
+    expected = File.read!("test/ApprovalTest.ThirtyDays.verified.txt")
+    assert capture_io(fn -> GildedRose.TextTestFixture.run(30) end) == expected
+  end
+
   test "begin the journey of refactoring" do
     items = [%Item{name: "foo", sell_in: 0, quality: 0}]
     GildedRose.update_quality(items)