RuleRefExpression extends NativeExpression { @Override public void execute(Machine machine) { throw new UnsupportedOperationException(); } RuleRefExpression(GrammarRuleKey ruleKey); GrammarRuleKey getRuleKey(); @Override void execute(Machine machine); @Override String toString();  }
@Test public void can_not_be_executed() { thrown.expect(UnsupportedOperationException.class); expression.execute(machine); }