First Ruby Gem!!!

I've just created my first Ruby Gem out of the with_probability code I've been working on. Simply

sudo gem install nondeterminism

Much thanks also to the initial author of the Sometimes Pastie Any problems with or suggestions for the gem? Join the Google Ruby-Nondeterminism Group

with_probability

In fuzzing my database for testing (see Fuzzing your Database and Faker), I've found the following to be very useful:

Object.class_eval do
  def with_probability(prob, &block)
    if rand <= prob
      block.call 
      return ProbabilisticDoer::Done.new
    else
      return ProbabilisticDoer::NotDone.new
    end
  end
end

module ProbabilisticDoer
  class NotDone
    def else_with_probability(prob, &block)
      with_probability(prob, &block)
    end
    def else(&block)
      with_probability(1, &block)
    end
  end
  
  class Done
    def else_with_probability(prob, &block)
      return self
    end
    def else(&block)
      return self
    end
  end
end

With that, you can do things like

u = User.create(...)
with_probability(9/10.0) do
  u.stuff_that_most_users_should_do
end

with_probability(0.01) do
  u.stuff_that_very_few_users_should_do
end.else_with_probability(0.2) do
  u.stuff_that_some_but_none_of_the_above_users_should_do
end.else do
  u.stuff_the_rest_of_the_users_should_do
end