我不太明白softwaretestingoracle的概念.它说:Anoracleisamechanismfordeterminingwhethertheprogramhaspassedorfailedatest.考虑以下代码://classthatshouldbetestedpublicintsum(inta,intb){returna+b;}//testclassstaticMaintester=newMain();@TestpublicvoidtestSum(){assertEquals("2+3is5",5,tester.sum(2,3));}应测试的类总是返回2个整数的总和。