# 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](https://github.com/cucumber/common/tree/main/messages#cucumber-messages).

## Overview

The kit is composed of features and messages:

- features, once executed, emit an exhaustive set of Messages as specified by
  the protocol
- Messages - serialized as `.ndjson` files - are the reference: a given feature
  from the kit, executed using its dedicated step definitions, must emit the
  corresponding Messages

The ruby gem also provides some tools to help in the validation of messages issued
from the execution of the CCK's features.

## 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:

```ruby
# spec/cck_spec.rb
require 'cucumber-compatibility-kit'

describe 'Cucumber Compatibility Kit' do
  let(:cucumber_bin) { './bin/cucumber' }
  let(:cucumber_common_args) { '--publish-quiet --profile none --format message' }
  let(:cucumber_command) { "#{cucumber_bin} #{cucumber_common_args}" }

  examples = Cucumber::CompatibilityKit.gherkin_examples.reject { |example|
    example == 'retry'
  }

  examples.each do |example_name|
    describe "'#{example_name}' example" do
      include_examples 'cucumber compatibility kit' do
        let(:example) { example_name }
        let(:messages) { `#{cucumber_command} --require #{example_path} #{example_path}` }
      end
    end
  end
end

```

`Cucumber::CompatibilityKit.gherkin_examples` returns an array that list all the
gherkin examples available within the CCK. Here, we want to execute all of them with
the exception of the `retry` one.

`let(:messages)` executes the cucumber command. `example_path` is provided by the
CCK. It is the path to the folder which contains the feature, and the support code
required to execute the given example. As we use the `--format message` formatter,
`messages` will then contain the messages as a `ndjson` document.

You can use `gem open cucumber-compatibility-kit` in order to take a look on the
features, their support code, and the expected messages.They are available in the
`features` folder within the gem.

## More info

The Cucumber Compatibility Kit is part of the development tools of [Cucumber](https://cucumber.io).
It allows us to make sure that all our implementations are properly supporting our internal protocol
and thus are compabitle with each other and with our common tools like the [html-formatter](https://github.com/cucumber/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](https://github.com/cucumber/compatibility-kit)
to get more help if you need to.

You can also take a look on [cucumber-ruby](https://github.com/cucumber/cucumber-ruby/blob/v8.0.0/spec/cck/cck_spec.rb)
to see how the kit is used there.