id_sequence_resetter.rb

class IDSequenceResetter
  def reset(connection)
    @cached_sql ||= {}
    sql = @cached_sql[connection] ||=
      begin
        sequences = connection.execute(%{SELECT c.relname FROM pg_class c WHERE c.relkind = 'S'}).values.flatten

        "".tap do |sql|
          sequences.each do |name|
            next if not name.ends_with?("id_seq")

            sql << %{ALTER SEQUENCE #{connection.quote_table_name(name)} RESTART WITH 1;\n}
          end
        end
     end

    connection.execute sql
  end
end

RSpec.configure do |config|
  id_sequence_resetter = IDSequenceResetter.new

  config.before do |example|
    id_sequence_resetter.reset(ActiveRecord::Base.connection)
    id_sequence_resetter.reset(RecordWithOtherDatabase.connection)
  end
end