Merge bitcoin#25670: test: check that combining PSBTs with different txs fails

4e616d2 test: check that combining PSBTs with different txs fails (Sebastian Falbesoner)
2a428c7 test: support passing PSBTMaps directly to PSBT ctor (Sebastian Falbesoner)

Pull request description:

  This PR adds missing test coverage for the `combinepsbt` RPC, in the case of combining two PSBTs with different transactions:
  https://github.com/bitcoin/bitcoin/blob/b8067cd435059eedb580975afc62c4e7a6f27321/src/psbt.cpp#L24-L27
  The calling function `CombinePSBTs` checks for the false return value and then returns the transaction error string `PSBT_MISMATCH`:
  https://github.com/bitcoin/bitcoin/blob/b8067cd435059eedb580975afc62c4e7a6f27321/src/psbt.cpp#L433-L435
  https://github.com/bitcoin/bitcoin/blob/b8067cd435059eedb580975afc62c4e7a6f27321/src/util/error.cpp#L30-L31

ACKs for top commit:
  instagibbs:
    reACK bitcoin@4e616d2
  achow101:
    ACK 4e616d2

Tree-SHA512: 45b2b224b13b44ad69ae62e4bc20f74cab32770cf8127b026ec47a7520f7253148fdbf1fad612afece59e45a6738bef9a351ae87ea98dc83d095cc78f6db0318

Author: achow101

test/functional/rpc_psbt.py

@@ -820,6 +820,16 @@ def test_psbt_input_keys(psbt_input, keys):
             assert hash.hex() in res_input[preimage_key]
             assert_equal(res_input[preimage_key][hash.hex()], preimage.hex())
 
+        self.log.info("Test that combining PSBTs with different transactions fails")
+        tx = CTransaction()
+        tx.vin = [CTxIn(outpoint=COutPoint(hash=int('aa' * 32, 16), n=0), scriptSig=b"")]
+        tx.vout = [CTxOut(nValue=0, scriptPubKey=b"")]
+        psbt1 = PSBT(g=PSBTMap({PSBT_GLOBAL_UNSIGNED_TX: tx.serialize()}), i=[PSBTMap()], o=[PSBTMap()]).to_base64()
+        tx.vout[0].nValue += 1  # slightly modify tx
+        psbt2 = PSBT(g=PSBTMap({PSBT_GLOBAL_UNSIGNED_TX: tx.serialize()}), i=[PSBTMap()], o=[PSBTMap()]).to_base64()
+        assert_raises_rpc_error(-8, "PSBTs not compatible (different transactions)", self.nodes[0].combinepsbt, [psbt1, psbt2])
+        assert_equal(self.nodes[0].combinepsbt([psbt1, psbt1]), psbt1)
+
 
 if __name__ == '__main__':
     PSBTTest().main()

test/functional/test_framework/psbt.py

@@ -96,10 +96,10 @@ def serialize(self):
 class PSBT:
     """Class for serializing and deserializing PSBTs"""
 
-    def __init__(self):
-        self.g = PSBTMap()
-        self.i = []
-        self.o = []
+    def __init__(self, *, g=None, i=None, o=None):
+        self.g = g if g is not None else PSBTMap()
+        self.i = i if i is not None else []
+        self.o = o if o is not None else []
         self.tx = None
 
     def deserialize(self, f):