Field Test

A/B testing that stores assignments in your database and shows the results in a
mounted dashboard.

What you get

• Experiments defined in a YAML file
• Variant assignment that survives the anonymous-to-signed-in transition
• Conversion tracking with one call
• A dashboard with Bayesian probability that each variant wins

Mounting it

# Gemfile
gem "field_test"

# config/routes.rb
authenticate :user, ->(user) { user.admin? } do
  mount FieldTest::Engine, at: "field_test"
end

<%%= field_test(:button_color) == "red" ? "Buy now" : "Get started" %>

The assignment problem, solved

The hard part of A/B testing is not splitting traffic — it is keeping a visitor in
the same bucket after they sign up. Field Test handles that because it can see both
the cookie and the user record.