Time travel steps

When /^(\d+) (minutes|hours|days) pass$/ do |amount, unit|
  now = Time.now
  Time.stubs(:now).returns(now + amount.to_i.send(unit.to_sym))
end

When /^going back (\d+) (minutes|hours|days)$/ do |minutes|
  now = Time.now
  Time.stubs(:now).returns(now - amount.to_i.send(unit.to_sym))
end