my $old_cache_count = $db->cache_count();
  my $data = $db->fetch('known key 1');
  ok( $data, 'expected value for key 1' );
  # we expect that to have caused a cache load
  my $new_cache_count = $db->cache_count();
  ok( $new_cache_count, $old_cache_count + 1 );

  $old_cache_count = $new_cache_count;
  $data = $db->fetch('known key 2');
  ok( $data, 'expected value for key 2' );
  # the cache shouldn't have reloaded
  ok( $db->cache_count(), $old_cache_count );