class RuboCop::Cop::RSpec::DescribedClass

def collapse_namespace(namespace, const)
  return const if namespace.empty? || const.first.nil?
  start = [0, (namespace.length - const.length)].max
  max = namespace.length
  intersection = (start..max).find do |shift|
    namespace[shift, max - shift] == const[0, max - shift]
  end
  [*namespace[0, intersection], *const]
end