Test txinwitness is accessible on coinbase vin

Author: rvagg

test/functional/feature_segwit.py

@@ -20,6 +20,7 @@
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import (
     assert_equal,
+    assert_is_hex_string,
     assert_raises_rpc_error,
     connect_nodes,
     hex_str_to_bytes,
@@ -193,6 +194,14 @@ def run_test(self):
             assert self.nodes[1].getrawtransaction(tx_id, False, blockhash) == self.nodes[2].gettransaction(tx_id)["hex"]
             assert self.nodes[0].getrawtransaction(tx_id, False, blockhash) == tx.serialize_without_witness().hex()
 
+        # Coinbase contains the witness commitment nonce, check that RPC shows us
+        coinbase_txid = self.nodes[2].getblock(blockhash)['tx'][0]
+        coinbase_tx = self.nodes[2].gettransaction(txid=coinbase_txid, verbose=True)
+        witnesses = coinbase_tx["decoded"]["vin"][0]["txinwitness"]
+        assert_equal(len(witnesses), 1)
+        assert_is_hex_string(witnesses[0])
+        assert_equal(witnesses[0], '00'*32)
+
         self.log.info("Verify witness txs without witness data are invalid after the fork")
         self.fail_accept(self.nodes[2], 'non-mandatory-script-verify-flag (Witness program hash mismatch)', wit_ids[NODE_2][P2WPKH][2], sign=False)
         self.fail_accept(self.nodes[2], 'non-mandatory-script-verify-flag (Witness program was passed an empty witness)', wit_ids[NODE_2][P2WSH][2], sign=False)