IMO "breaking-in" and reliability testing are two different things:
- "Breaking-in" means the process of getting the different moving metal parts of the gun to wear against each other in such a manner as to burnish smooth or mate their engagement surfaces together. IMO this does not constitute reliability testing per se, but rather a final "work-fitting" of assembled parts; IIRC, the ultra-high-end Les Baer 1911's are assembled to such tight tolerances(ostensibly in order to maintain a high degree of mechanical accuracy over the service life of the gun) that the manufacturer specifically instructs their customers to fire 200-300 rds through the gun before cleaning off the factory lube - otherwise, the slide/barrel/frame fit will be so tight that manually operating the gun will be very difficult.
- Reliability testing, OTOH, is simply the process of proving that your gun will function with your chosen ammunition to your satisfaction. Whether that process takes one box of your chosen carry JHP ammo, or over a thousand rounds of mixed brands/bullet types, is immaterial - so long as YOU, the person who will be carrying said gun to protect yourself and/or your loved ones, are satisfied that your gun/ammo combination will work. Having said that, if your gun/ammo combo works perfectly for a minimum of 200 rds, you have empirical proof that said combo has a reliability rating between 99.5%-to-100%, which is mathematically close enough to perfect that you needn't test beyond 200 rds unless our peace of mind(or OCD) requires it.
- No matter how good the manufacturer's reputation/gun-magazine reviews/on-line range reports/gun-store recommendations are, it is up to YOU to test-fire YOUR gun to make sure it works - your gun may have been the last one made on a Friday, or the first one made on a Monday, by the least-experienced trainee on the production floor, from parts supplied by a vendor with out-of-date specs, etc. If you don't, yes, your family might have a heck of a lawsuit - BUT YOU'LL BE IN THE HOSPITAL OR THE CEMETERY. Even then, they might not win; IIRC a pizza-store manager lost a lawsuit against Glock several years ago because he admitted that he had not cleaned or test-fired the gun nor taken any formal training before he fired one round in self-defense - and then limp-wrist-jammed the gun.
- I don't have it in front of me, but IIRC Duane Thomas' article in the Aug/06 S.W.A.T. Magazine, "Replacement Guns: A Backup for Training and More" makes an interesting point in that if a gun is going to fail due to defective parts or sub-assemblies, it will do so within the first 1000 rds; once the construction/assembly/fitting of the gun has been thus "proved," then the gun can be expected to work reliably for thousands more rounds, until certain parts(springs, extractors, pins, etc.) reach the end of their service life - at that point, if the gun happens to malfunction, the root cause will not be a manufacturing defect, but rather a failure on the user's part to properly maintain the gun by replacing parts worn by thousands of rounds of use.