There were so many combinations that normal manual testing methods would have taken more than a hundred years.
组合如此之多，以正常的人工检测方式，需要一百多年的时间。
英语百科
Manual testing
Compare with Test automation.
Manual testing is the process of manually testing software for defects. It requires a tester to play the role of an end user and use most of all features of the application to ensure correct behavior. To ensure completeness of testing, the tester often follows a written test plan that leads them through a set of important test cases.