test.rb

require 'thread'

root = File.expand_path('../lib/constants', __FILE__)

constants = Queue.new
numbers   = (1..5000).to_a

numbers.shuffle.each do |number|
  name   = "B#{number}"
  path   = File.join(root, "b#{number}.rb")

  a_path   = File.join(root, "a#{number}.rb")
  a_number = numbers.sample

  File.open(path, 'w') do |handle|
    handle.puts <<-EOF
class #{name}
  autoload :A#{a_number}, #{a_path.inspect}
end
    EOF
  end

  constants << name

  Object.autoload(name, path)
end

numbers.shuffle.each do |number|
  name = "A#{number}"
  path = File.join(root, "a#{number}.rb")

  File.open(path, 'w') do |handle|
    handle.puts <<-EOF
class #{name}
end

A#{numbers.sample}
    EOF
  end

  constants << name

  Object.autoload(name, path)
end

Thread.abort_on_exception = true

threads = 50.times.map do
  Thread.new do
    loop do
      break if constants.size == 0

      Object.const_get(constants.pop)
    end
  end
end

threads.each(&:join)