Reuse Cucumber steps

Best wrap your steps in %{} rather than quotes. Then, you don't need to escape double quotes which you'll need to use frequently.:

Given /^I login successfully$
  step %{I login with valid credentials}
end

Given /^I login with (.*) credentials$/ |type|
  # do stuff with type being one of "invalid" or "valid"
end

Calling steps from step definitions is a bad practice and has some disadvantages:

1. If scenario will fail and there are nested step invocations, you will get only the last invoked step definition in the stack trace. It may be hard to find from which place that last stepdef was called
2. Call to stepdef is sometimes harder to find and read than ruby method
3. Ruby methods give you more power than calling steps from step defs

Aslak Hellesøy recommends to extract popular actions to World instead of reusing steps. It isolates those actions in one place, makes this code easier to find. You can extract code to usual Ruby classes or modules as well.

#/support/world_extensions.rb
module KnowsUser
  def login
    visit('/login')
    fill_in('User name', with: user.name)
    fill_in('Password', with: user.password)
    click_button('Log in')
  end

  def user
    @user ||= User.create!(:name => 'Aslak', :password => 'xyz')
  end
end
World(KnowsUser)

#/step_definitions/authentication_steps.rb
When /^I login$/ do
  login
end

Given /^a logged in user$/ do
  login
end

Here is a useful discussion on the subject in Cucumber mailing list - link

Note that the method for calling steps within steps has changed in recent versions of cucumber, which you'll see if you get an error like "WARNING: Using 'Given/When/Then' in step definitions is deprecated, use 'step' to call other steps instead:/path/to/step_definitions/foo_steps.rb:631:in `block in ' ". See the cucumber wiki for details.

The gist of the change is that you should now use the step or steps methods.

When /^I make all my stuff shiny$/
  step "I polish my first thing"
end

When /^I make all my stuff shiny$/
  steps %Q{
    When I polish my first thing
    When I shine my second thing
  }
end

UPDATE: The method described below has been deprecated. The recommended way to call a step from within another step now looks like this:

Given /^I login successfully$/
    step "I login with valid credentials" 
end 

---

Old, deprecated method (for reference):

You can call steps from other steps like this:

Given /^I login successfully$/
  Given "I login with valid credentials"
  Then "I should be logged in"
end

If all of the scenarios within a feature require this (or other steps), you can also add a Background to each features, with the common steps, like so:

Background:
  Given I log in with valid credentials

Scenario: Change my password
  Given I am on the account page