Use ExceptionGroup instead of printing, improve changelog

changelog/11728.improvement.rst

@@ -1 +1 @@
-Class cleanup exceptions are now reported.
+For ``unittest``-based tests, exceptions during class cleanup (as raised by functions registered with :meth:`TestCase.addClassCleanup <unittest.TestCase.addClassCleanup>`) are now reported instead of silently failing.

src/_pytest/unittest.py

@@ -32,6 +32,9 @@ from _pytest.runner import CallInfo
 import pytest
 
 
+if sys.version_info[:2] < (3, 11):
+    from exceptiongroup import BaseExceptionGroup
+
 if TYPE_CHECKING:
     import unittest
 
@@ -111,18 +114,19 @@ class UnitTestCase(Class):
             return None
         cleanup = getattr(cls, "doClassCleanups", lambda: None)
 
-        def process_teardown_exceptions(raise_last: bool):
-            errors = getattr(cls, "tearDown_exceptions", None)
-            if not errors:
+        def process_teardown_exceptions() -> None:
+            # tearDown_exceptions is a list set in the class containing exc_infos for errors during
+            # teardown for the class.
+            exc_infos = getattr(cls, "tearDown_exceptions", None)
+            if not exc_infos:
                 return
-            others = errors[:-1] if raise_last else errors
-            if others:
-                num = len(errors)
-                for n, (exc_type, exc, tb) in enumerate(others, start=1):
-                    print(f"\nclass cleanup error ({n} of {num}):", file=sys.stderr)
-                    traceback.print_exception(exc_type, exc, tb)
-            if raise_last:
-                raise errors[-1][1]
+            exceptions = [exc for (_, exc, _) in exc_infos]
+            # If a single exception, raise it directly as this provides a more readable
+            # error.
+            if len(exceptions) == 1:
+                raise exceptions[0]
+            else:
+                raise BaseExceptionGroup("Unittest class cleanup errors", exceptions)
 
         def unittest_setup_class_fixture(
             request: FixtureRequest,
@@ -138,7 +142,7 @@ class UnitTestCase(Class):
                 # follow this here.
                 except Exception:
                     cleanup()
-                    process_teardown_exceptions(raise_last=False)
+                    process_teardown_exceptions()
                     raise
             yield
             try:
@@ -146,7 +150,7 @@ class UnitTestCase(Class):
                     teardown()
             finally:
                 cleanup()
-                process_teardown_exceptions(raise_last=True)
+                process_teardown_exceptions()
 
         self.session._fixturemanager._register_fixture(
             # Use a unique name to speed up lookup.

testing/test_unittest.py

@@ -1500,7 +1500,15 @@ def test_do_cleanups_on_teardown_failure(pytester: Pytester) -> None:
     assert passed == 1
 
 
-def test_class_cleanups_failure_in_setup(pytester: Pytester) -> None:
+class TestClassCleanupErrors:
+    """
+    Make sure to show exceptions raised during class cleanup function (those registered
+    via addClassCleanup()).
+
+    See #11728.
+    """
+
+    def test_class_cleanups_failure_in_setup(self, pytester: Pytester) -> None:
         testpath = pytester.makepyfile(
             """
             import unittest
@@ -1518,12 +1526,11 @@ def test_class_cleanups_failure_in_setup(pytester: Pytester) -> None:
         )
         result = pytester.runpytest("-s", testpath)
         result.assert_outcomes(passed=0, errors=1)
-    result.stderr.fnmatch_lines(
+        result.stdout.fnmatch_lines(
             [
-            "class cleanup error (1 of 2):",
-            "Exception: fail 1",
-            "class cleanup error (2 of 2):",
-            "Exception: fail 2",
+                "*Unittest class cleanup errors *2 sub-exceptions*",
+                "*Exception: fail 1",
+                "*Exception: fail 2",
             ]
         )
         result.stdout.fnmatch_lines(
@@ -1533,8 +1540,7 @@ def test_class_cleanups_failure_in_setup(pytester: Pytester) -> None:
             ]
         )
 
-
-def test_class_cleanups_failure_in_teardown(pytester: Pytester) -> None:
+    def test_class_cleanups_failure_in_teardown(self, pytester: Pytester) -> None:
         testpath = pytester.makepyfile(
             """
             import unittest
@@ -1551,17 +1557,34 @@ def test_class_cleanups_failure_in_teardown(pytester: Pytester) -> None:
         )
         result = pytester.runpytest("-s", testpath)
         result.assert_outcomes(passed=1, errors=1)
-    result.stderr.fnmatch_lines(
-        [
-            "class cleanup error (1 of 2):",
-            "Traceback *",
-            "Exception: fail 1",
-        ]
-    )
         result.stdout.fnmatch_lines(
             [
-            "* ERROR at teardown of MyTestCase.test *",
-            "E * Exception: fail 2",
+                "*Unittest class cleanup errors *2 sub-exceptions*",
+                "*Exception: fail 1",
+                "*Exception: fail 2",
+            ]
+        )
+
+    def test_class_cleanup_1_failure_in_teardown(self, pytester: Pytester) -> None:
+        testpath = pytester.makepyfile(
+            """
+            import unittest
+            class MyTestCase(unittest.TestCase):
+                @classmethod
+                def setUpClass(cls):
+                    def cleanup(n):
+                        raise Exception(f"fail {n}")
+                    cls.addClassCleanup(cleanup, 1)
+                def test(self):
+                    pass
+        """
+        )
+        result = pytester.runpytest("-s", testpath)
+        result.assert_outcomes(passed=1, errors=1)
+        result.stdout.fnmatch_lines(
+            [
+                "*ERROR at teardown of MyTestCase.test*",
+                "*Exception: fail 1",
             ]
         )