I run 3 DNS servers for various domains I buy/transfer on my customers behalf.
Before I transfer a domain, I configure my servers so that they are ready to serve requests for that domain, using a copy of the current DNS records. My registrar is configured to automatically set my DNS servers as glue records upon domain transfer.
When the transfer happens it does not matter how slow the NS glue records propagate, because other records are just the same between old and new DNS servers: I can just sit and wait while everything works on my customer side.
A problem arises when I make a mistake configuring my servers before the trasfer. I can only run basic tests against my servers and visually check the results, but, since the domain is not transferred yet, it's hard to test every requisite the registrar wants to actually set my servers as NS for the domain.
Things get worse when you consider that different TLDs have different registrars, and different sets of rules about the DNS health.
Is there anything like intodns.com and similar services, that lets me specify the IP address of the DNS to check, even if that IP address is not one of the current NS records, that runs the tests pretending the IP address were actually part of the configured NS records?