contract-example.rb

module Test
  module RGB
    include Kit::Contract

    before ->(r:, g:, b:) { (0..255) === r && (0..255) === g && (0..255) === b }
    after  [
      ->(result:) { result.is_a?(String) },
      ->(result:) { result.start_with?('#') },
      ->(result:) { result.length.in?([4, 7]) },
    ]
    def self.rgb_to_hex(r:, g:, b:)
      "+" << [r, g, b].map { |el| el.to_s(16).rjust(2, '0') }.join
    end
  end
end

Test::RGB.rgb_to_hex(r: 128, g: 32, b: 12)

#RuntimeError:
#  Kit::Contracts | after failure for `Test::RGB.rgb_to_hex`
#    ["/Users/nathan/bootcamp/elearning/code/kit/libs/kit-organizer/spec/rgb_spec.rb", 11] ->(result:) { result.start_with?('#') },
#    Called with: {:result=>"+80200c"}