tests: add tests for CLI

Signed-off-by: Henry Schreiner <henryfs@princeton.edu>

Author: henryiii

src/packaging/tags.py

@@ -114,10 +114,7 @@ def __str__(self) -> str:
         return f"{self._interpreter}-{self._abi}-{self._platform}"
 
     def __repr__(self) -> str:
-        return (
-            f"{self.__class__.__name__}"
-            f"({self._interpreter!r}, {self._abi!r}, {self._platform!r})"
-        )
+        return f"<{self} @ {id(self)}>"
 
     def __setstate__(self, state: tuple[None, dict[str, Any]]) -> None:
         # The cached _hash is wrong when unpickling.

src/packaging/version.py

@@ -931,9 +931,9 @@ def _cmpkey(
     return epoch, _release, _pre, _post, _dev, _local
 
 
-if __name__ == "__main__":
-    import argparse
-    import operator
+def main() -> None:
+    import argparse  # noqa: PLC0415
+    import operator  # noqa: PLC0415
 
     operations = {
         "lt": operator.lt,
@@ -971,3 +971,7 @@ def _cmpkey(
     if args.command == "compare":
         result = operations[args.operator](args.version1, args.version2)
         raise SystemExit(not result)
+
+
+if __name__ == "__main__":
+    main()

tests/test_version_cli.py

@@ -0,0 +1,60 @@
+# This file is dual licensed under the terms of the Apache License, Version
+# 2.0, and the BSD License. See the LICENSE file in the root of this repository
+# for complete details.
+
+from __future__ import annotations
+
+import sys
+
+import pytest
+
+from packaging.version import main
+
+
+@pytest.mark.parametrize(
+    ("args", "retcode"),
+    [
+        ("1.2 eq 1.2", 0),
+        ("1.2 eq 1.2.0", 0),
+        ("1.2 eq 1.2dev1", 1),
+        ("1.2 == 1.2", 0),
+        ("1.2 == 1.2.0", 0),
+        ("1.2 == 1.2dev1", 1),
+        ("1.2 ne 1.2.0", 1),
+        ("1.2 ne 1.2dev1", 0),
+        ("1.2 != 1.2.0", 1),
+        ("1.2 != 1.2dev1", 0),
+        ("1.2 lt 1.2.0", 1),
+        ("1.2 lt 1.2dev1", 1),
+        ("1.2 lt 1.3", 0),
+        ("1.2 < 1.2.0", 1),
+        ("1.2 < 1.2dev1", 1),
+        ("1.2 < 1.3", 0),
+        ("1.2 gt 1.2.0", 1),
+        ("1.2 gt 1.2dev1", 0),
+        ("1.2 gt 1.1", 0),
+        ("1.2 > 1.2.0", 1),
+        ("1.2 > 1.2dev1", 0),
+        ("1.2 > 1.1", 0),
+        ("1.2 le 1.2", 0),
+        ("1.2 le 1.3", 0),
+        ("1.2 le 1.1", 1),
+        ("1.2 <= 1.2", 0),
+        ("1.2 <= 1.3", 0),
+        ("1.2 <= 1.1", 1),
+        ("1.2 ge 1.2", 0),
+        ("1.2 ge 1.1", 0),
+        ("1.2 ge 1.3", 1),
+        ("1.2 >= 1.2", 0),
+        ("1.2 >= 1.1", 0),
+        ("1.2 >= 1.3", 1),
+        ("1.2 foo 1.2", 2),
+        ("1.2 == unreal", 2),
+    ],
+)
+def test_compare(monkeypatch: pytest.MonkeyPatch, args: str, retcode: int) -> None:
+    monkeypatch.setattr(sys, "argv", ["prog", "compare", *args.split()])
+    with pytest.raises(SystemExit) as excinfo:
+        main()
+
+    assert excinfo.value.code == retcode