tracks/features/step_definitions/login_steps.rb

Given /^I have logged in as "(.*)" with password "(.*)"$/ do |username, password|
  visit login_path
  fill_in "Login", :with => username
  fill_in "Password", :with => password
  click_button
  response.should contain(/Login successful/)
  @current_user = User.find_by_login(username)
end

When /^I submit the login form as user "([^\"]*)" with password "([^\"]*)"$/ do |username, password|
  fill_in 'Login', :with => username
  fill_in 'Password', :with => password
  click_button
end