Set up a containerized feature testing framework (DDR-2428). Aspects of this framework include:
- A selenium standalone Chrome docker image for test environment
- Capybara, configured to use the remote selenium container for any JS tests
- Starter test fixture files for a collection, item, & component in DC
- Rake tasks ddr_xenon:seed:fixtures, ddr_xenon:test:default, & ddr_xenon:test:accessibility
- Refactors guard_production! check for shared use by fixture & sample data tasks
- Adds some basic RSpec feature tests, some using JS, others not
- Adds some basic accessibility tests using axe-core-rspec matchers
- Adds Makefile command 'make accessibility'
- GitLab CI stage for accessibility tests (allowed to fail)