The purpose of the test program the F-35 is going through now is specifically to find faults, so that they can be corrected before it goes into production. Here I'd mention things like communications. You may not recall this, but the F-18 had some communications challenges, specifically in the north. The F-18 had cold weather challenges. The F-18 had fatigue cracking.
Is it fair to say that the purpose of test programs is precisely to find those things? They shouldn't be taken to mean that the airplane will never do something because it failed it in the test program, but the purpose of the test program is to find those things so they can be fixed and the airplane, like the F-18, will perform brilliantly for decades.