Is there an active testnet for Bitcoin Cash?
Yes, there is.  After many hours I eventually received blocks up to the present time.  

There is a working DNS seed at testnet-seed-abc.bitcoinforks.org (hardcoded in the Bitcoin ABC source) which lists active Bitcoin Cash testnet nodes, many of which actually work.  Bitcoin ABC doesn't seem to prefer this seed - it tries lots of others that only have Bitcoin Core testnet nodes - but you can do manually do dig testnet-seed-abc.bitcoinforks.org and then addnode the resulting IP addresses.