You may have encountered a bug in the Ruby interpreter or extension libraries.
Running an exercise on building a web app from the book Agile web development for Rails 5
command bin/rails test test/controllers/line_items/controller_test.rb
and I get the attached crash
Mac OSX 10.12
ruby version - ruby 2.3.1p112 (2016-04-26 revision 54768) [x86_64-darwin16]
rails version 220.127.116.11