Question: I am trying to run a rake test and I am unable to do it. I keep getting this error:
ActiveRecord::SchemaMigration Load (0.1ms) SELECT "schema\_migrations".\* FROM "schema\_migrations"
rake aborted!
LoadError: cannot load such file -- rails/performance\_test\_help

I would greatly appreciate any insight.

Answer: 
[`rails/performance_test_help`](https://github.com/rails/rails/blob/v3.2.21/railties/lib/rails/performance_test_help.rb) is an old test helper that was used up to Rails 3.2 [for performance testing](http://guides.rubyonrails.org/v3.2.13/performance_testing.html). It was supposed to be required by performance test cases.

The file was remove in Rails 4 since the performance testing feature was extracted from Rails core and moved to the [rails-perftest](https://rubygems.org/gems/rails-perftest) gem.

If you are using Rails 4, make sure the gem is listed in your `Gemfile`, and it's correctly installed. If you don't use the feature, simply drop the performance test cases.

To lookup the offending file, simply search your project codebase for any `require 'rails/performance_test_help'` statement, and either fix the issue or remove the offending file if you don't need the performance test case.
run `rake db:migrate RAILS_ENV=test` before running rake test. Hope this solves your problem.