> That's a bad argument. You can also never be certain any third-party code works at all
Perhaps in the philosophical sense that you can never be certain of anything, this is true. But that only place that thinking leads is to staying under the covers all day.
You actually can achieve a high degree of certainty that third-party code works to some reasonable standard by testing it. Which is the whole point - once you have tested a version, and are content that it works, you wouldn't want to blindly switch to another version without again performing a similar set of tests.
Perhaps in the philosophical sense that you can never be certain of anything, this is true. But that only place that thinking leads is to staying under the covers all day.
You actually can achieve a high degree of certainty that third-party code works to some reasonable standard by testing it. Which is the whole point - once you have tested a version, and are content that it works, you wouldn't want to blindly switch to another version without again performing a similar set of tests.