Testing only proves that the circuit with those particular components work under those conditions that day. The only way to make a reliable thing is by design.

Dear Erik,

There must be more behind the above statement which is not obvious...

When you say "reliable design", I suppose that you stick to the fundamental electronic principles, device data sheet recommendations, standards if any and safety guidelines. OK having done all this the thing still HAS to be tested to finally see if it meets requirement. Assume you notice a defeciency and it gets solved ONLY by a deviation to data sheet recomendation.

Now the million dollar question :

Allow the product to ship as it has passed testing
(OR)
Wait for design validation of the change that was done by the Chip manufacturer ?

Going by your statement, the second option is the way to go. But this as you know will not happen if there are no big volumes / OEM application etc..

I am not posting this as a matter of general interest -happens to us quite often when whole machines are ready for despatch.

Raghu