module ExitCodeMatchers
  RSpec::Matchers.define :exit_with_code do |code|
    actual = nil

    match do |block|
      begin
        block.call
      rescue SystemExit => e
        actual = e.status
      end
      actual and actual == code
    end

    failure_message_for_should do |block|
      "expected block to call exit(#{code}) but exit" +
        (actual.nil? ? " not called" : "(#{actual}) was called")
    end

    failure_message_for_should_not do |block|
      "expected block not to call exit(#{code})"
    end

    description do
      "expect block to call exit(#{code})"
    end
  end
end