Update Readme Files

tests/test_hashing.py

@@ -24,3 +24,16 @@ def test_hash_password_with_algorithm_parameter():
     """Verify hash_password accepts algorithm parameter."""
     salt, hashed = hash_password("test", algorithm="pbkdf2")
     assert verify_password("test", salt, hashed, algorithm="pbkdf2")
+
+
+def test_backward_compatibility_with_old_pbkdf2_hashes():
+    """Verify existing PBKDF2 hashes still work without algorithm parameter."""
+    # Simulate old hash created before algorithm parameter existed
+    salt, hashed = hash_password("legacy-password")
+
+    # Verify using old API (no algorithm parameter)
+    assert verify_password("legacy-password", salt, hashed)
+    assert not verify_password("wrong", salt, hashed)
+
+    # Verify using new API with explicit pbkdf2
+    assert verify_password("legacy-password", salt, hashed, algorithm="pbkdf2")