Experimental is an Split testing framework for Rails.
It was written with a few goals in mind:
- Split the users in a non-predictable pattern (i.e. half of the users won't always be in all experiments)
- Keep experiments and their start and end dates in the database
- Have a clear developer workflow, so that tests in the code are started in the database when the code goes out and tests that should be removed make the site explode
- Allow admins to end experiments and set a winner
- Cache the experiments
rails g experimental
For the class you'd like to be the subject of experiments, include the Experimental::Subject module in a model with an id and timestamps
class User < ActiveRecord::Base include Experimental::Subject # ... end
Create an experiment
config/experimental.yml, add the name, num_buckets, and notes of the
experiment under in_code:
in_code: - name: :price_experiment num_buckets: 2 notes: | 0: $22 1: $19.99
Using the experiment
To see if a user is in the experiment population AND in a bucket:
# checks if the user is in the my_experiment population # and if they are in bucket 0 user.in_bucket?(:my_experiment, 0)
To see if a user is in the experiment population ONLY
user.in_experiment?(:my_experiment) user.not_in_experiment?(:my_experiment) # inverse
To see which bucket of an experiment a user is in:
Ending an experiment
You can end an experiment by setting the end_date. In the admin interface, there is a dropdown to set the end date. When ending an experiment you must set a winning bucket
Ending an experiment means that all users will be given the winning bucket
Removing an experiment
A removed experiment is an experiment that is not referenced anywhere in code. In fact, the framework will throw an exception if you reference an experiment that is not in code.
Removing an experiment from
config/experimental.yml and running
rake experimental:sync will remove the experiment and expire the cache.
removed: - name: :price_experiment
In your test suite, you typically want to have an neutral starting state across all your tests. For experiments, this means all subjects are out of all experiments. You then opt a particular subject into a particular bucket for any experiment as your test requires.
Experimental ships with support to do this in a number of popular test frameworks. Setup instructions for each framework are in the following sections.
Once set up, you can then force a subject into a bucket for an experiment as follows:
set_experimental_bucket(subject, :my_experiment, 1)
If you set the bucket (1 in the above example) to
nil, this means set the
subject to be out of the experiment (the default state).
require 'experimental/test/unit' class MyTest < Test::Unit::TestCase include Experimental::Test::Unit ... end
Note that if you define a
setup method, then you must remember to call
super (always good practice in general).
require 'experimental/test/rspec' RSpec.configure do |config| config.include Experimental::Test::RSpec end
Experiments can be defined in
Running the rake task
rake experimental:sync will load those
experiments under 'in_code' into the database and set removed_at
timestamp for those under 'removed'
You will likely want to automate the running of
rake experimental:sync by adding to your deploy file.
When you deploy, simply invoke the experimental:sync Rake task to update the experiments in your database from the configuration file:
after 'deploy:updated', 'experimental:sync' do on primary :worker do within release_path do rake experimental:sync end end end
Admin created experiments
The purpose of Admin created experiments are for experiments that will flow through to another system, such as an email provider. They likely start with a known string and are dynamically sent in code. Otherwise, Admin created experiments will do nothing as there is no code attached to them.