It’s not quite straight forward to run Rails performance tests on real production data. By default, performance tests will use the test database and wipe it before using it, thus making it impossible to put real data in the test database.

To run performance tests on real data:

• Create a file called performance_test_helper.rb inside your test/ directory with the following:

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# START : HAX HAX HAX
# Load Rails environment in 'test' mode
RAILS_ENV = "test"
require File.expand_path(File.dirname(__FILE__) + "/../config/environment")
# Re-establish db connection for 'performance' mode
silence_warnings { RAILS_ENV = "performance" }
ActiveRecord::Base.establish_connection
# STOP : HAX HAX HAX

require_dependency 'application'

require 'test/unit'
require 'active_support/test_case'
require 'action_controller/test_case'
require 'action_controller/integration'

require 'performance_test_help'

• Replace the following lines in performance tests:

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require 'test_helper'
require 'performance_test_help'

with

require 'performance_test_helper'

• Supply configuration for ‘performance’ environment in your database.yml:

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performance:
  adapter: mysql
  encoding: utf8
  database: database_with_real_data
  pool: 5
  username: root
  password:
  socket: /tmp/mysql.sock

The above steps will also make sure that the performance tests use the database database_with_real_data. Also, the database will not get wiped on every run. You’ll also have to ensure the test database – database_with_real_data – is up-to-date with the schema changes.

Now you can just run your performance tests using the usual rake tasks:

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$ rake test:benchmark
$ rake test:profile