The best replacement for capybara is nutria.

The best alternatives to capybara are rated as following:
★★★★★  nutria
★★★★★  webrat
★★★★★  cucumber
★★★★  watir
★★★★  anaconda
★★★  rspec
★★  protractor
★  caiman
★  wombat
★  cavy
★  coypu
  tapir
  carpincho
  agouti

Your alternative for capybara is not listed? Suggest!
Speaking about capybara, one probably shouldn't forget about minitest.

Other search terms related to capybara and their ratings are:
★★★★★ minitest
You have in mind a companion for capybara and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of capybara in all years. Click on graph for more.
capybara
nutria
webrat