Step Argument Transforms

Step argument transforms help your step definitions be more DRY. You can use the Transform method to register a regular expression along with a code block. Before captured regex groups get yielded as arguments to step definitions, an attempt is made to match them against any registered Transform. If there is a match, the return value of the block supplied with the transform is yielded as the step definition argument instead. Here is an example:

# support file
Transform /^user \w+$/ do |step_arg|
  User.find_by_username /(\w+)$/.match(step_arg)[0]
end

# step definition file
Then /^(user \w+) should be friends with (user \w+)$/ do |user, friend|
  support_user.work_queue.should include(customer_user)
end

# feature file
Scenario: support assigned a customer
  Given ...
  When ...
  Then user larrytheliquid should be friends with user dastels

One key thing to remember is to provide some contextual data like “user” so you don’t end up transforming every single argument to a step definition. For a more detailed explanation and examples, see the following blog post:
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