@Test
public void relational() throws Exception {

  Expression expression = parseExpression("5 gt 5");
  assertEquals("{5 GT 5}", expression.toString());
  expression = parseExpression("5 ge 5");
  assertEquals("{5 GE 5}", expression.toString());
  expression = parseExpression("5 lt 5");
  assertEquals("{5 LT 5}", expression.toString());
  expression = parseExpression("5 le 5");
  assertEquals("{5 LE 5}", expression.toString());
  assertEquals("{5 LE 5.1}", parseExpression("5 le 5.1").toString());
  assertEquals("{1 GT null}", parseExpression("1 gt null").toString());
  assertEquals("{null GE 2}", parseExpression("null ge 2").toString());
  assertEquals("{null LE null}", parseExpression("null le null").toString());
  wrongExpression("5 gt duration'PT5H'");
}