Basic unit tests for Versioned implementations.

tests/unit/test_versioning.py

@@ -0,0 +1,77 @@
+"""
+ This file is part of nucypher.
+
+ nucypher is free software: you can redistribute it and/or modify
+ it under the terms of the GNU Affero General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+
+ nucypher is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ GNU Affero General Public License for more details.
+
+ You should have received a copy of the GNU Affero General Public License
+ along with nucypher.  If not, see <https://www.gnu.org/licenses/>.
+"""
+
+from nucypher.utilities.versioning import Versioned
+import pytest
+
+
+class A(Versioned):
+
+    def __init__(self, x):
+        self.x = x
+
+    @classmethod
+    def _brand(cls):
+        return b"AA"
+
+    @classmethod
+    def _version(cls):
+        return 2
+
+    def _payload(self) -> bytes:
+        return bytes(self.x)
+
+    @classmethod
+    def _old_version_handlers(cls):
+        return {1: cls._from_bytes_v1}
+
+    @classmethod
+    def _from_bytes_v1(cls, data):
+        return cls(int(data))  # we used to keep it in decimal representation
+
+    @classmethod
+    def _from_bytes_current(cls, data):
+        return cls(int(data, 16))  # but now we switched to the hexadecimal
+
+
+def test_versioning_header_prepend():
+    a = A(1)  # stake sauce
+    serialized = bytes(a)
+    header = serialized[:Versioned._HEADER_SIZE]
+    brand = header[:Versioned._BRAND_LENGTH]
+    assert brand == A._brand()
+    version = header[Versioned._BRAND_LENGTH:]
+    version_number = int.from_bytes(version, 'big')
+    assert version_number == A._version()
+
+
+def test_versioning_brand():
+    invalid = b'\x00\x03\x00\x0112'
+    with pytest.raises(Versioned.InvalidHeader, match="Incompatible bytes for A."):
+        A.from_bytes(invalid)
+    incorrect = b'AB\x00\x0112'
+    with pytest.raises(Versioned.InvalidHeader, match="Incorrect brand. Expected b'AA', Got b'AB'."):
+        A.from_bytes(incorrect)
+
+
+def test_versioning_handlers():
+    s1 = b'AA\x00\x0112'
+    s2 = b'AA\x00\x0212'
+    a1 = A.from_bytes(s1)
+    assert a1.x == 12
+    a2 = A.from_bytes(s2)
+    assert a2.x == 18