Cleanup CaptureWarnings after_run

Author: bf4

test/test_helper.rb

@@ -17,9 +17,10 @@
 require 'capture_warnings'
 @capture_warnings = CaptureWarnings.new(fail_build = false)
 @capture_warnings.before_tests
-at_exit do
+Minitest.after_run do
   @capture_warnings.after_tests
 end
+
 require 'active_model_serializers'
 
 require 'support/stream_capture'