The dawn-v3.0.0 is currently latest stable tag to be used on Testnet.
However it has a major bug that could kill Testnet nodes using empty array in query:
https://github.com/EOSIO/eos/issues/2277
Until a next stable tag is out - you will want to apply the fix manually to proof your node from this failure with the fix: https://github.com/EOSIO/eos/pull/2297/files
Just add in file: libraries/chain/contracts/abi_serializer.cpp on lines:
#317 if (va.size() > 0) {
...
#325 }
And recompile!
We are applying this bug fix on Arrowhead Testnet for all nodes:
https://busy.org/@eluzgin/how-to-join-arrowhead-testnet-for-bp-candidates
