Start bitcoind on mainnet, let it run out of IBD. Park a block shortly before the most recent checkpoint:
`src/bitcoin-cli parkblock 00000000000000000036e1c7ca4d2c0d3de84fc5ba2a720a226eb14ab612ec0f`
Check the result with the `getchaintips` RPC.
Stop and restart `bitcoind`, verify that the entire chain is unparked with `getchaintips`.
Look for the log message // Unparking checkpointed block 00000000000000000b360176b8456de45b662fce6d557c6238dec17362d197f3 ...// (this is the hash of the most recent checkpoint).