@Test
public void multiplicative() throws Exception {

  Expression expression = parseExpression("5 mul 5");
  assertEquals("{5 MUL 5}", expression.toString());
  expression = parseExpression("5 div 5");
  assertEquals("{5 DIV 5}", expression.toString());
  expression = parseExpression("5 mod 5");
  assertEquals("{5 MOD 5}", expression.toString());
  wrongExpression("1 mod '2'");
}