The Cucumber Compatibility Kit for Ruby

The CCK - aka. Cucumber Compatibility Kit - is a set of features and Messages. It aims to validate an implementation of the Cucumber Messages protocol.


This kit (gem), consists of a set of features, miscellaneous files and messages:

  • Each area will contain one feature, which, once executed, will emit an exhaustive set of messages as specified by the protocol
  • Some of these areas may "also" require miscellaneous files to be used when testing functions such as attaching images or documents or reading data from files
  • Each area will contain a set of messages - serialized as a single .ndjson file This is the reference for the CCK, that a given feature from the kit, when executed using any dedicated step definitions, must emit the exact corresponding messages

Installation and Usage

Add cucumber-compatibility-kit to your Gemfile as a development dependency, and install it:

bundle install

Then add a spec that could look like this:

# spec/my_compatibility_checks_spec.rb
require 'cucumber-compatibility-kit'

describe 'Cucumber Compatibility Kit', type: :feature do
  let(:cucumber_command) { 'bundle exec cucumber --publish-quiet --profile none --format message' }

  # Don't run the retry or skipped CCK Examples (For whatever reason)
  examples = CCK::Examples.gherkin.reject { |example| example == 'retry' || example == 'skipped' }

  examples.each do |example_name|
    describe "'#{example_name}' example" do
      include_examples 'cucumber compatibility kit' do
        let(:example) { example_name }
        # You will need to specify the relative support code and cck paths
        let(:messages) { `#{cucumber_command} --require #{support_code_path} #{cck_path}` }

CCK::Examples.gherkin will return an array that lists all the gherkin examples available within the CCK. Here, we want to execute all of them with the exception of the retry and skipped ones.

let(:messages) will execute the cucumber command. As we are using the message formatter, messages will then contain the messages as a ndjson document with one message per line.

You can use gem open cucumber-compatibility-kit in order to take a look at the features and the expected messages they should produce. They are available in the features folder within the gem.

More info

The Cucumber Compatibility Kit is part of the development tools of Cucumber. It allows us to make sure that all our implementations are properly supporting our internal protocol and thus are compatible (and consistent), with each other and our common tools like the html-formatter.

It can be a valuable tool if you are developing integration with cucumber, or your own implementation of it.

Join us on github/cucumber/compatibility-kit to get more help if you need to.

You can also take a look on cucumber-ruby to see how the kit is used there.


Before building this project locally, the samples must be copied from the devkit. Use:

cd ../devkit
npm ci && npm run copy-to:ruby
cd ../ruby