Add BIP32 HD wallet regression tests

Added regression tests for BIP32 HD wallet functionality, including master serialization, child derivation, and error handling for invalid segments.

Author: Pymmdrza

tests/test_bip32.py

@@ -0,0 +1,39 @@
+"""BIP32 HD wallet regression tests."""
+from __future__ import annotations
+
+import pytest
+
+from libcrypto.bip32 import BIP32Error, HDWallet
+
+
+SEED = bytes.fromhex("000102030405060708090a0b0c0d0e0f")
+MASTER_XPRV = (
+    "xprv9s21ZrQH143K3QTDL4LXw2F7HEK3wJUD2nW2nRk4stbPy6cq3jPPqjiChkVv"
+    "vNKmPGJxWUtg6LnF5kejMRNNU3TGtRBeJgk33yuGBxrMPHi"
+)
+CHILD_XPRV = (
+    "xprv9wTYmMFdV23N2TdNG573QoEsfRrWKQgWeibmLntzniatZvR9BmLnvSxqu53K"
+    "w1UmYPxLgboyZQaXwTCg8MSY3H2EU4pWcQDnRnrVA1xe8fs"
+)
+
+
+def test_master_serialization_matches_reference() -> None:
+    """Master node serialization should match the official BIP32 test vector."""
+    wallet = HDWallet(SEED)
+    assert wallet.master_node.serialize_private() == MASTER_XPRV
+
+
+def test_child_derivation_matches_reference() -> None:
+    """Deriving m/0'/1 should match the corresponding reference xprv."""
+    wallet = HDWallet(SEED)
+    child = wallet.derive_from_path("m/0'/1")
+
+    assert child.serialize_private() == CHILD_XPRV
+
+
+def test_derivation_rejects_invalid_segment() -> None:
+    """Invalid derivation strings must raise BIP32Error."""
+    wallet = HDWallet(SEED)
+
+    with pytest.raises(BIP32Error):
+        wallet.derive_from_path("m/44'/0'/abc")