function testTree_IndexRangeScan_CrossColumnIndex_Unaffected() {
  var treeBefore =
      'project()\n' +
      '-order_by(CrossColumnTable.string ASC, CrossColumnTable.number DESC)\n' +
      '--select(value_pred(CrossColumnTable.boolean eq false))\n' +
      '---table_access_by_row_id(CrossColumnTable)\n' +
      '----index_range_scan(CrossColumnTable.idx_crossColumn, ' +
          '[unbound, unbound],[unbound, 10], natural)\n';

  lf.testing.treeutil.assertTreeTransformation(
      constructTree3(lf.Order.ASC, lf.Order.DESC),
      treeBefore, treeBefore, pass);
}
Tests the case where an existing IndexRangeScanStep can't be leveraged to
perform the ORDER BY, because the requested order does not much neither the
reverse nor the natural index's order.