As of writing, there are 25 active witnesses in testnet is ready for the hard fork:
abit-test, blckchnd-testnet, clockwork.witness-1, sahkan-bts-testnet, sc-bitshares-testnet, zhaomu-test, witness.zapata, bangzi-test, crazybit.witness, xeldal-test, roelandp, witness-still, witness.yao.test, thom-witness, freedom-t, sampson-test, test-hiblockchain, migicwallet-witness,fox-20180510,delegate.ihashfury,lafona-testnet,oxarbitrage-test,initX,gdex-witness,necklace-w,bhuz-testnet,rngl4b
Their witness account in mainnet are:
in.abit, blckchnd, clockwork, sahkan-bitshares, sc-ol, delegate-zhaomu, ?, bangzi, crazybit, xeldal, roelandp, witness.still, witness.yao, verbaltech2, delegate.freedom, winex.witness, witness.hiblockchain, magicwallet.witness, fox, delegate.ihashfury, delegate-1.lafona, ?, ?, gdex-witness, xn-delegate,bhuz,rnglab
Among them,
* sc-ol, bangzi have witness accounts in mainnet, but are not active (didn't get voted in);
* witness.zapata, initX(xeroc), oxarbitrage-test(oxarbitrage) don't have an witness account in mainnet.
These active mainnet witnesses don't have an active witness in testnet:
bhuz, rnglab, abc123, xman, openledger-dc, elmato, mr.agsexplorer
Update: bhuz updated.
Update: rnglab had updated earlier