Doubt that any exchange will risk it with listing a coin that is still on testnet, qtrade was an exception
A lot of coins are being listed before mainnet. AE, THETA, IOTX, IOST, ZIL, ENIGMA, QLC - those are only few coins out of dozens that i remember to be go on mainnet while being actively traded on binance, priced 60M $ - 1,2B $. Enigma was listed on binance in 10/2017, started
testnet in 03/2019 (?) - 1.5 year with ETH placeholder.