How does Cucumber find supporting code?

The directories scanned for steps are determined by the feature file(s)/directories passed to the cucumber command. Cucumber will look in the sub-directories of the feature files

features
  billing
    credit_card.feature
  scoring
    multi_player.feature
    single_player.feature
  step_definitions
    billing_steps.rb
    scoring_steps.rb

Cucumber will run correctly from the features directory, but if you want to run a single feature you need to pass the -r, --require command line argument:

$ cucumber billing/credit_card.feature -r features

This is taken from the Cucumber book