use async: false in tests with File.cd!

Author: josevalim

test/ecto/migration_test.exs

@@ -1,8 +1,6 @@
 defmodule Ecto.MigrationTest do
-  # Although this test uses the Ecto.Migration.Runner which
-  # is global state, we can run it async as long as this is
-  # the only test case that uses the Runner in async mode.
-  use ExUnit.Case, async: true
+  # We use in_tmp which uses File.cd!
+  use ExUnit.Case, async: false
   use Ecto.Migration
 
   import Support.FileHelpers

test/ecto/migrator_test.exs

@@ -1,5 +1,6 @@
 defmodule Ecto.MigratorTest do
-  use ExUnit.Case
+  # We use in_tmp which uses File.cd!
+  use ExUnit.Case, async: false
 
   import Support.FileHelpers
   import Ecto.Migrator