How can I force estimatesmartfee to return estimates on regtest? Creating an app that utilizes estimatesmartfee, and it works in production, but I use regtest for automated testing and can't get it to return a value.

Looking at bitcoind tests it is splitting UTXOs in a loop etc.

What is the bare minimum I need to do as far as dummy transactions and mining blocks in order to get estimatesmartfee to work like it does on mainnet.

Thanks.
You need to fill up the mempool of your regtest nodes and mine blocks (this means creating transactions --eg by using sendtoaddress-- and generating blocks --with generatoaddress).
For reference here is how it's done to test estimatesmartfee.