cucumber-ruby/examples/tcl/features/step_definitions/fib_steps.rb

When(/^I ask Tcl to calculate fibonacci for (\d+)$/) do |n|
  @fib_result = @fib.eval("fib #{n}").to_i
end

Then(/^it should give me (\d+)$/) do |expected|
  expect(@fib_result).to eq expected.to_i
end