Helper class to identify which classes are leaking in unit tests

myspec.rb

  before(:all) do
    @stats = OStats.new filters: ['Grape'], suppress_nodelta: true
    @stats.collect!
  end

  after(:all) do
    @stats.collect!
    @stats.display
  end

Sample output

Grape::Route                                                         87 delta         71
Grape::Util::HashStack                                               68 delta         28
Grape::Endpoint                                                      56 delta         29
Grape::Request                                                        1 delta          1
Grape::Cookies                                                        1 delta          1

spec_helper.rb

# Based on http://johansorensen.com/articles/finding-leaking-ruby-objects.html
# and https://groups.google.com/d/msg/comp.lang.ruby/KvUdmQSsf-U/Vn-yDUoWt2EJ

  class OStats
    def initialize options
      @filters = (options.delete :filters) || ['']
      @suppress_nodelta = options.delete :suppress_nodelta
      @stats = Array.new
    end

    def collect!
      stats = Hash.new(0)

      ObjectSpace.each_object do |o|
        @filters.each do |f|
          stats[o.class] += 1 if o.class.name.start_with? f
        end
      end

      @stats << stats
    end

    def display
      @stats[-1].sort {|(k1,v1),(k2,v2)| v2 <=> v1}.each do |k,v|
        delta = ((v - @stats[-2][k]) unless @stats[-2].nil?) || 0
        if !@suppress_nodelta or delta != 0
          printf "%-60s %10d", k, v
          if !@suppress_nodelta or delta != 0
            printf " delta %10d", delta
          end
          puts
        end
      end
    end
  end