Use null logger in test; keep track of original logger

Author: bf4

test/logger_test.rb

@@ -2,7 +2,7 @@
 
 class ActiveModelSerializers::LoggerTest < Minitest::Test
   def test_logger_is_set_to_action_controller_logger_when_initializer_runs
-    assert_equal ActiveModelSerializers.logger, ActionController::Base.logger
+    assert_equal $action_controller_logger, ActionController::Base.logger # rubocop:disable Style/GlobalVars
   end
 
   def test_logger_can_be_set

test/test_helper.rb

@@ -63,3 +63,8 @@ def Minitest.after_run(&block)
 require 'fixtures/active_record'
 
 require 'fixtures/poro'
+
+ActiveSupport.on_load(:active_model_serializers) do
+  $action_controller_logger = ActiveModelSerializers.logger # rubocop:disable Style/GlobalVars
+  ActiveModelSerializers.logger = Logger.new(IO::NULL)
+end