arghh.rb

require 'json'
require 'objspace'
require 'fileutils'
require 'stringio'
require 'pp'

FileUtils.mkdir_p("tmp")

ObjectSpace.trace_object_allocations_start

$addresses = []

def run
  string = "i am a string #{rand(0..100)}"
  $addresses << "0x#{ (string.object_id << 1).to_s(16) }"
  puts "Address of string is: #{$address}"

  string.singleton_class.instance_eval do
  end

  string
  return nil
end

run
run
run
run

# ===== CALLING GC HERE =====

GC.start

# ===========================

File.open('tmp/heap.json','w') do |f|
  ObjectSpace.dump_all(output: f)
end

output = File.readlines('tmp/heap.json')
actual = output.map.select do |line|
  if $addresses.include?(JSON.parse(line)["address"])
    puts "Found in heap dump:"
    puts "  #{line}"
    true
  end
end.length

expected = 1
result   = expected == actual ? "PASS" : "FAIL"
puts "\n#{result} expected: #{expected} actual: #{actual}"

exit(1) unless expected == actual