Was curious about some DNS entropy and other DNS related things and came across some tools to test DNS.
This one will test with random long sub-domain names. Apparently some routers will crash.
https://www.grc.com/dns/crashtest.htm
This one is customizalbe test and will run for a while.
https://www.grc.com/dns/customtest.htm
This is some general info about publically available DNS servers.
https://www.grc.com/dns/alternatives.htm
Some offer parental controls, some hijack nxdomain responses, etc.
Some just give honest answers.