Add test case test_zero_fingerprint_handling

diff --git a/tests/test_psbt_parser.py b/tests/test_psbt_parser.py
index 897b753..bdfdf86 100644
--- a/tests/test_psbt_parser.py
+++ b/tests/test_psbt_parser.py
@@ -149,6 +149,74 @@ class TestPSBTParser:
             assert PSBTParser.has_matching_input_fingerprint(psbt, PSBTTestData.multisig_key_3)
 
 
+    def test_zero_fingerprint_handling(self):
+        """
+        PSBTParser should correctly handle PSBTs with zero fingerprints (created from XPUB-only imports, 
+        without derivation path) by matching public keys against the seed and filling in correct fingerprints.
+        """
+        for input in PSBTTestData.ALL_INPUTS:
+            psbt = PSBT.parse(a2b_base64(input))
+            
+            # Backup original derivations
+            original_derivations = []
+            original_taproot_derivations = []
+            for inp in psbt.inputs:
+                for pub, derivation in inp.bip32_derivations.items():
+                    original_derivations.append((pub, derivation))
+
+                for pub, (leaf_hashes, derivation) in inp.taproot_bip32_derivations.items():
+                    original_taproot_derivations.append((pub, leaf_hashes, derivation))
+            
+            # Set fingerprints to zero to simulate XPUB-only import
+            from embit.psbt import DerivationPath
+            for inp in psbt.inputs:
+                for pub, derivation in inp.bip32_derivations.items():
+                    inp.bip32_derivations[pub] = DerivationPath(
+                        fingerprint=b"\x00\x00\x00\x00",
+                        derivation=derivation.derivation
+                    )
+
+                for pub, (leaf_hashes, derivation) in inp.taproot_bip32_derivations.items():
+                    inp.taproot_bip32_derivations[pub] = (leaf_hashes, DerivationPath(
+                        fingerprint=b"\x00\x00\x00\x00",
+                        derivation=derivation.derivation
+                    ))
+            
+            # Verify that has_matching_input_fingerprint works with zero fingerprints
+            # This tests the fallback mechanism that tries to derive and match pubkeys
+            assert PSBTParser.has_matching_input_fingerprint(psbt, PSBTTestData.seed, SettingsConstants.REGTEST)
+            
+            # Test that it correctly rejects wrong seeds
+            wrong_seed = Seed(["bacon"] * 24)
+            assert PSBTParser.has_matching_input_fingerprint(psbt, wrong_seed, SettingsConstants.REGTEST) == False
+            
+            # Test the PSBTParser's ability to fill zero fingerprints during parsing
+            parser = PSBTParser(p=psbt, seed=PSBTTestData.seed, network=SettingsConstants.REGTEST)
+            
+            # Verify fingerprints were correctly filled after parsing
+            seed_fingerprint = parser.seed.get_fingerprint(SettingsConstants.REGTEST)
+            fingerprints_filled = False
+            
+            for inp in parser.psbt.inputs:
+                for pub, derivation in inp.bip32_derivations.items():
+                    if derivation.fingerprint != b"\x00\x00\x00\x00":
+                        fingerprints_filled = True
+                        # Should match the seed's fingerprint
+                        from binascii import hexlify
+                        assert hexlify(derivation.fingerprint).decode() == seed_fingerprint
+                
+                # Also check Taproot derivations
+                for pub, (leaf_hashes, derivation) in inp.taproot_bip32_derivations.items():
+                    if derivation.fingerprint != b"\x00\x00\x00\x00":
+                        fingerprints_filled = True
+                        # Should match the seed's fingerprint
+                        from binascii import hexlify
+                        assert hexlify(derivation.fingerprint).decode() == seed_fingerprint
+            
+            # Fingerprints should have been filled
+            assert fingerprints_filled > 0
+
+
     def test_trim_and_sig_count(self):
         """
         PSBTParser should correctly trim a psbt of all unnecessary data and count the number of