Chips these days are generally designed to be tested before they're packaged - maybe not at speed but usually some scan vectors and a sanity check for current u

Chips these days are generally designed to be tested before they're packaged - maybe not at speed but usually some scan vectors and a sanity check for current usage. Time spent on a tester (a machine costing ~$1M+) is expensive, so is packaging a chip - so typically one does a quick sanity test before packaging and a longer test afterwards. For chiplets one is more likely to do more early testing, because the packaging is likely to be more expensive (along with all the other dies in the package)