Add static type assertions to is_platform test

Author: EliahKagan

test/deprecation/test_compat.py

@@ -11,6 +11,11 @@
 import os
 import sys
 
+if sys.version_info >= (3, 11):
+    from typing import assert_type
+else:
+    from typing_extensions import assert_type
+
 import pytest
 
 import git.compat
@@ -38,6 +43,10 @@ def test_is_platform() -> None:
         is_posix = git.compat.is_posix
         is_darwin = git.compat.is_darwin
 
+    assert_type(is_win, bool)
+    assert_type(is_posix, bool)
+    assert_type(is_darwin, bool)
+
     messages = [str(entry.message) for entry in ctx]
     assert len(messages) == 3