Merge pull request #455 from allenap/preserve-type-when-using-fixture

Preserve type when using fixture

Author: jelmer

testtools/compat.py

@@ -16,13 +16,14 @@
 import locale
 import os
 import sys
+import typing
 import unicodedata
 
 # Ensure retro-compatibility with older testtools releases
 from io import BytesIO, StringIO
 
 
-def reraise(exc_class, exc_obj, exc_tb, _marker=object()):
+def reraise(exc_class, exc_obj, exc_tb, _marker=object()) -> typing.NoReturn:
     """Re-raise an exception received from sys.exc_info() or similar."""
     raise exc_obj.with_traceback(exc_tb)
 

testtools/testcase.py

@@ -21,6 +21,7 @@
 import sys
 import types
 import unittest
+from typing import Any, Protocol, TypeVar
 from unittest.case import SkipTest
 
 from testtools import content
@@ -168,6 +169,15 @@ def gather_details(source_dict, target_dict):
 fixtures = try_import("fixtures")
 
 
+class UseFixtureProtocol(Protocol):
+    def setUp(self) -> Any: ...
+    def cleanUp(self) -> Any: ...
+    def getDetails(self) -> dict[str, content.Content]: ...
+
+
+UseFixtureT = TypeVar("UseFixtureT", bound=UseFixtureProtocol)
+
+
 def _mods(i, mod):
     (q, r) = divmod(i, mod)
     while True:
@@ -729,7 +739,7 @@ def _run_test_method(self, result):
         """
         return self._get_test_method()()
 
-    def useFixture(self, fixture):
+    def useFixture(self, fixture: UseFixtureT) -> UseFixtureT:
         """Use fixture in a test case.
 
         The fixture will be setUp, and self.addCleanup(fixture.cleanUp) called.