function testBothColumnsIndexed() {
  var treeBefore =
      'project()\n' +
      '-join(type: inner, impl: hash, join_pred(TableA.id eq TableB.id))\n' +
      '--table_access(TableA)\n' +
      '--table_access(TableB)\n';

  var treeAfter =
      'project()\n' +
      '-join(type: inner, impl: index_nested_loop, ' +
          'join_pred(TableA.id eq TableB.id))\n' +
      '--table_access(TableA)\n' +
      '--no_op_step(TableB)\n';

  lf.testing.treeutil.assertTreeTransformation(
      constructTree1(
          schema.table('TableA'), schema.table('TableB'), false),
      treeBefore, treeAfter, pass);
}
Tests a simple tree, where
 - Only one join predicate exists.
 - Both columns of the join predicate have an index.
 - The columns in the join predicate appear in the same order as the tables
   of the join, left TableA, right TableB.