@Test
public void resolve_ref_expression() {

  BindingTuple bindingTuple =
      ExprValueUtils.tupleValue(ImmutableMap.of("ip", "209.160.24.63")).bindingTuples();
  assertEquals(ExprValueUtils.stringValue("209.160.24.63"),
      bindingTuple.resolve(DSL.ref("ip", STRING)));
}