Testnet Test Vectors?

[ChristopherA]

Could you add some testnet vectors to your README.md and tests.c?

We have a prototype txid to txref tool in C for our DID:BTCR hackathon, that calls bitcoind's RPC through libbitcoinrpc, however it requires a full node with --txindex. We are largely testing our stuff on testnet, so we can't test to see if we have any errors in our implementation: https://github.com/WebOfTrustInfo/btcr-hackathon/tree/master/txid2bech32

We also welcome any coding and security advice on this C app — it is clunky ;-)