Update test_framework/psbt.py for PSBTv2

diff --git a/contrib/signet/miner b/contrib/signet/miner
index f46d88b5..1d9f8720 100755
--- a/contrib/signet/miner
+++ b/contrib/signet/miner
@@ -66,8 +66,8 @@ def signet_txs(block, challenge):
 def decode_challenge_psbt(b64psbt):
     psbt = PSBT.from_base64(b64psbt)
 
-    assert len(psbt.tx.vin) == 1
-    assert len(psbt.tx.vout) == 1
+    assert len(psbt.i) == 1
+    assert len(psbt.o) == 1
     assert PSBT_SIGNET_BLOCK in psbt.g.map
     return psbt
 
diff --git a/test/functional/test_framework/psbt.py b/test/functional/test_framework/psbt.py
index 0a57be31..b43669a5 100644
--- a/test/functional/test_framework/psbt.py
+++ b/test/functional/test_framework/psbt.py
@@ -4,11 +4,15 @@
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 import base64
+import struct
+
+from io import BytesIO
 
 from .util import assert_equal
 from .messages import (
     CTransaction,
     deser_string,
+    deser_compact_size,
     from_binary,
     ser_compact_size,
 )
@@ -108,37 +112,81 @@ class PSBT:
         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
+        self.version = None
 
     def deserialize(self, f):
         assert_equal(f.read(5), b"psbt\xff")
         self.g = from_binary(PSBTMap, f)
-        assert PSBT_GLOBAL_UNSIGNED_TX in self.g.map
-        self.tx = from_binary(CTransaction, self.g.map[PSBT_GLOBAL_UNSIGNED_TX])
-        self.i = [from_binary(PSBTMap, f) for _ in self.tx.vin]
-        self.o = [from_binary(PSBTMap, f) for _ in self.tx.vout]
+
+        self.version = 0
+        if PSBT_GLOBAL_VERSION in self.g.map:
+            self.version = struct.unpack("<I", self.g.map[PSBT_GLOBAL_VERSION])[0]
+            assert self.version in [0, 2]
+        if self.version == 2:
+            assert PSBT_GLOBAL_INPUT_COUNT in self.g.map
+            assert PSBT_GLOBAL_OUTPUT_COUNT in self.g.map
+            in_count = deser_compact_size(BytesIO(self.g.map[PSBT_GLOBAL_INPUT_COUNT]))
+            out_count = deser_compact_size(BytesIO(self.g.map[PSBT_GLOBAL_OUTPUT_COUNT]))
+        else:
+            assert PSBT_GLOBAL_UNSIGNED_TX in self.g.map
+            tx = from_binary(CTransaction, self.g.map[PSBT_GLOBAL_UNSIGNED_TX])
+            in_count = len(tx.vin)
+            out_count = len(tx.vout)
+
+        self.i = [from_binary(PSBTMap, f) for _ in range(in_count)]
+        self.o = [from_binary(PSBTMap, f) for _ in range(out_count)]
         return self
 
     def serialize(self):
         assert isinstance(self.g, PSBTMap)
         assert isinstance(self.i, list) and all(isinstance(x, PSBTMap) for x in self.i)
         assert isinstance(self.o, list) and all(isinstance(x, PSBTMap) for x in self.o)
-        assert PSBT_GLOBAL_UNSIGNED_TX in self.g.map
-        tx = from_binary(CTransaction, self.g.map[PSBT_GLOBAL_UNSIGNED_TX])
-        assert_equal(len(tx.vin), len(self.i))
-        assert_equal(len(tx.vout), len(self.o))
+        if self.version is not None and self.version == 2:
+            self.g.map[PSBT_GLOBAL_INPUT_COUNT] = ser_compact_size(len(self.i))
+            self.g.map[PSBT_GLOBAL_OUTPUT_COUNT] = ser_compact_size(len(self.o))
+        if self.version is None or (self.version is not None and self.version == 0):
+            assert PSBT_GLOBAL_UNSIGNED_TX in self.g.map
+            tx = from_binary(CTransaction, self.g.map[PSBT_GLOBAL_UNSIGNED_TX])
+            assert_equal(len(tx.vin), len(self.i))
+            assert_equal(len(tx.vout), len(self.o))
 
         psbt = [x.serialize() for x in [self.g] + self.i + self.o]
         return b"psbt\xff" + b"".join(psbt)
 
     def make_blank(self):
         """
-        Remove all fields except for PSBT_GLOBAL_UNSIGNED_TX
+        Remove all fields except for required fields depending on version
         """
-        for m in self.i + self.o:
-            m.map.clear()
-
-        self.g = PSBTMap(map={PSBT_GLOBAL_UNSIGNED_TX: self.g.map[PSBT_GLOBAL_UNSIGNED_TX]})
+        if self.version == 0:
+            for m in self.i + self.o:
+                m.map.clear()
+
+            self.g = PSBTMap(map={PSBT_GLOBAL_UNSIGNED_TX: self.g.map[PSBT_GLOBAL_UNSIGNED_TX]})
+        elif self.version == 2:
+            self.g = PSBTMap(map={
+                PSBT_GLOBAL_TX_VERSION: self.g.map[PSBT_GLOBAL_TX_VERSION],
+                PSBT_GLOBAL_INPUT_COUNT: self.g.map[PSBT_GLOBAL_INPUT_COUNT],
+                PSBT_GLOBAL_OUTPUT_COUNT: self.g.map[PSBT_GLOBAL_OUTPUT_COUNT],
+                PSBT_GLOBAL_VERSION: self.g.map[PSBT_GLOBAL_VERSION],
+            })
+
+            new_i = []
+            for m in self.i:
+                new_i.append(PSBTMap(map={
+                    PSBT_IN_PREVIOUS_TXID: m.map[PSBT_IN_PREVIOUS_TXID],
+                    PSBT_IN_OUTPUT_INDEX: m.map[PSBT_IN_OUTPUT_INDEX],
+                }))
+            self.i = new_i
+
+            new_o = []
+            for m in self.o:
+                new_o.append(PSBTMap(map={
+                    PSBT_OUT_SCRIPT: m.map[PSBT_OUT_SCRIPT],
+                    PSBT_OUT_AMOUNT: m.map[PSBT_OUT_AMOUNT],
+                }))
+            self.o = new_o
+        else:
+            assert False
 
     def to_base64(self):
         return base64.b64encode(self.serialize()).decode("utf8")