test nonozero mac validation

binpickle/format.py

@@ -180,7 +180,7 @@ def decode(cls, buf: bytes | bytearray | memoryview, *, verify: bool = True) ->
         """
         off, len, ck, mac = TRAILER_FORMAT.unpack(buf)
         if verify and mac != b"\0" * 32:
-            raise ValueError("nonzero MACs not supported")
+            raise FormatError("nonzero MACs not supported")
         return cls(off, len, ck, mac)
 
 

tests/test_validation.py

@@ -13,11 +13,38 @@
 import pytest
 
 from binpickle import BinPickleFile, dump
-from binpickle.errors import IntegrityError
+from binpickle.errors import FormatError, IntegrityError
 
 _log = logging.getLogger(__name__)
 
 
+def test_verfy_unsupported_mac(tmp_path, rng: np.random.Generator):
+    "Nonzero MAC should fail"
+    file = tmp_path / "data.bpk"
+
+    df = pd.DataFrame(
+        {
+            "key": np.arange(0, 5000),
+            "count": rng.integers(0, 1000, 5000),
+            "score": rng.normal(10, 2, 5000),
+        }
+    )
+
+    dump(df, file, codecs=["lz4"])
+
+    # corrupt the file
+    stat = os.stat(file)
+    _log.info("%s: length %d", file, stat.st_size)
+    with open(file, "r+b") as f:
+        f.seek(stat.st_size - 4)
+        f.write(b"XX")
+
+    # try to read the file
+    with pytest.raises(FormatError, match=r"nonzero MACs"):
+        with BinPickleFile(file) as _bpf:
+            pass
+
+
 def test_verfy_index(tmp_path, rng: np.random.Generator):
     "Index hash mismatch should fail"
     file = tmp_path / "data.bpk"