Property-Based Testing in Ruby

A property-based testing tool for Ruby, utilizing Ractor for parallelizing test cases.

Installation

Install the gem and add to the application's Gemfile by executing:

$ bundle add pbt

If bundler is not being used to manage dependencies, install the gem by executing:

$ gem install pbt

Usage

# Let's say you have a method that returns just even numbers.
def twice(number)
  number * 2
end

RSpec.describe Pbt do
  it "works" do
    # The given block is executed 100 times with different random numbers.
    # Besides, the block runs in parallel by Ractor.
    Pbt.forall(Pbt::Generator.integer) do |number|
      result = twice(number)
      raise "Result should be even number" if result % 2 != 0
    end

    # If the function has a bug, the test fails with a counterexample.
    # Pbt::CaseFailure:
    #   RuntimeError:
    #   Failed on:
    #            0.5
  end
end

TODOs

[ ] More generators
- https://proper-testing.github.io/apidocs/
[ ] Enable to combine generators
- e.g. Pbt::Generator.list(Pbt::Generator.integer)
[ ] More sophisticated syntax for property-based testing
- e.g. forall(integer) { |number| ... } (Omit Pbt module)
[ ] Support for shrinking
[ ] Allow to use assertions
- It's hard to pass assertions like expect, assert to a Ractor?

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/[USERNAME]/pbt. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the code of conduct.

License

The gem is available as open source under the terms of the MIT License.

Code of Conduct

Everyone interacting in the Pbt project's codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.