Warnings rely on stdio and should be sync

Author: José Valim

lib/elixir/test/elixir/kernel/warning_test.exs

@@ -1,8 +1,7 @@
 Code.require_file "../test_helper.exs", __DIR__
 
 defmodule Kernel.WarningTest do
-  use ExUnit.Case, async: true
-
+  use ExUnit.Case
   import ExUnit.CaptureIO
 
   defp capture_err(fun) do

lib/elixir/test/elixir/system_test.exs

@@ -43,11 +43,6 @@ defmodule SystemTest do
     assert args == ["-o", "opt", "arg1", "arg2", "--long-opt", "10"]
   end
 
-  test :at_exit do
-    output = elixir('-e "System.at_exit(fn x -> IO.inspect x end)"')
-    assert output == '0\n'
-  end
-
   test :env do
     assert System.get_env("SYSTEM_ELIXIR_ENV_TEST_VAR") == nil
     System.put_env("SYSTEM_ELIXIR_ENV_TEST_VAR", "SAMPLE")