How do I send_keys a down arrow in capybara

If I remember correctly the correct way to send the down arrow command is to use arrow_down

So your code should look like this

listbox-example.native.sendkeys :arrow_down

If you would like a list of all the available keys that you can send, then docs are your friend here

http://www.ruby-doc.org/gems/docs/f/frameworks-capybara-0.2.18/SendKeys.html

EDIT: This link might have the intended content. https://www.omniref.com/ruby/gems/frameworks-capybara/0.2.18/symbols/SendKeys