# File lib/database_cleaner/truncation_base.rb, line 4
    def initialize(options = {})
      if !options.empty? && !(options.keys - [:only, :except]).empty?
        raise ArgumentError, "The only valid options are :only and :except. You specified #{options.keys.join(',')}."
      end
      if options.has_key?(:only) && options.has_key?(:except)
        raise ArgumentError, "You may only specify either :only or :either.  Doing both doesn't really make sense does it?"
      end

      @only = options[:only]
      @tables_to_exclude = (options[:except] || [])
      if migration_storage = migration_storage_name
        @tables_to_exclude << migration_storage
      end
    end