How confirm my own doublespend transaction got confirmed Transactions in the testnet are right now almost always double spent with a new txid (possible due to tx malleability). This is actually quite nice for testing purposes. 

So I'm wondering - when I did a payment and have txId 'XXX' this payment sometimes gets confirmed with a new txId 'YYY' that I don't know of. How can I (using bitcoind json-rpc) find out that my payment with txId 'XXX' got confirmed?
The answer is actually that you will receive a negative confirmation count in this case. (The bitcoin documentation is just terrible..)

See the bitcoin core release notes of 0.12.0 - section "Wallet: Negative confirmations and conflict detection"

https://bitcoin.org/en/release/v0.12.0

update note: In case of a negative confirmation (conflict detected) be sure to fetch all parent tx of that tx and see if that one got confirmed