@Test
public void unary() throws Exception {

  Expression expression = parseExpression("-5");
  assertEquals("-5", expression.toString());
  assertEquals("{MINUS -1}", parseExpression("--1").toString());
  assertEquals("{MINUS duration'PT1M'}", parseExpression("-duration'PT1M'").toString());
  expression = parseExpression("not false");
  assertEquals("{NOT false}", expression.toString());
  wrongExpression("not 11:12:13");
}