Well, the thing that stops you is the cost of designing, implementing, maintaining, and scaling the replica testbed. On a large network, that would be pretty hard to justify to most organizations, which would see it as very costly with a tough-to-measure upside.
Have you done this before? I'd be interested to hear how those conversations went.
For an organization like CF? Yes, I would expect them to have testing and network simulations down to an art.
If I had to guess, I'd say it's because network engineers simply don't need / get this know-how on normal scale. Most SW developers on the other hand are not very good (good enough for CF scale) at networking. Which leads to networking guys doing their thing the way it was always done... (hope I didn't offend anyone, just guessing)
I hope they strengthen their dev department... I know I'd love a challenge like that. :)
I have to wonder if it would have. Unless you have some kind of route visibility collecting took, or a bunch of simulated traffic sufficient to pop the CPU on the vMX that represented atl01, it would all appear to work. I wonder if you could generate traffic, and scrape snmp counters as a proxy?
Or some kind of tool that processes the resultant routing tables to generate some kind of "route usage" for every given link and device, maybe even feed it with a table of expected traffic to given destinations.
Have you done this before? I'd be interested to hear how those conversations went.