def coverage(local_type = nil, opts = {})
        local_type ||= opts.key?(:override_type) ? opts[:override_type] : type
        data = memcached.read(type_base_key(local_type))
        data = data ? JSON.parse(data) : {}
        data.delete_if { |file_path, file_data| file_hash(file_path) != file_data["file_hash"] } unless opts[:skip_hash_check]