How can I set up RSpec for performance testing 'on the side'

Question

We are using RSpec in a rails project for unit testing. I would like to set up some performance tests in RSpec, but do it in a way as to not disrupt the 'regular' features and fixtures.

Ideally I'd be able to tag my performance specs in a certain way such that they are not run by default. Then when I specify to run these specs explicitly it will load a different set of fixtures (it makes sense to do performance testing with a much larger and more 'production-like' dataset).

Is this possible? It seems like it should be.

Has anyone set up something like this? How did you go about it?

Answer 1

I managed to get what I was looking for via the following:

# Exclude :performance tagged specs by default
config.filter_run_excluding :performance => true

# When we're running a performance test load the test fixures:
config.before(:all, :performance => true) do
  # load performance fixtures
  require 'active_record/fixtures'
  ActiveRecord::Fixtures.reset_cache
  ActiveRecord::Fixtures.create_fixtures('spec/perf_fixtures', File.basename("products.yml", '.*'))
  ActiveRecord::Fixtures.create_fixtures('spec/perf_fixtures', File.basename("ingredients.yml", '.*'))
end

# define an rspec helper for takes_less_than
require 'benchmark'
RSpec::Matchers.define :take_less_than do |n|
  chain :seconds do; end
  match do |block|
    @elapsed = Benchmark.realtime do
      block.call
    end
    @elapsed <= n
  end
end

# example of a performance test
describe Api::ProductsController, "API Products controller", :performance do
  it "should fetch all the products reasonably quickly" do
    expect do
      get :index, :format => :json
    end.to take_less_than(60).seconds
  end
end

But I tend to agree with Marnen's point that this isn't really the best idea for performance testing.