Speed up rspec-rails tests by taming Ruby Garbage Collection From https://ariejan.net/2011/09/24/rspec-speed-up-by-tweaking-ruby-garbage-collection

deferred_garbage_collection.rb

class DeferredGarbageCollection

  DEFERRED_GC_THRESHOLD = (ENV['DEFER_GC'] || 15.0).to_f

  @@last_gc_run = Time.now

  def self.start

    GC.disable if DEFERRED_GC_THRESHOLD > 0

  end

  def self.reconsider

    if DEFERRED_GC_THRESHOLD > 0 && Time.now - @@last_gc_run >= DEFERRED_GC_THRESHOLD

      GC.enable
      GC.start
      GC.disable
      @@last_gc_run = Time.now

    end

  end

end

spec_helper.rb

RSpec.configure do |config|

  config.before(:all) do
    DeferredGarbageCollection.start
  end

  config.after(:all) do
    DeferredGarbageCollection.reconsider
  end

end