Bug report

If an exception is raised with a self-referencing __cause__ or __context__ then TestResult._clean_tracebacks() in result.py enters an infinite loop.

Minimal example 1:

try:raiseException()exceptExceptionase:raiseefrome

Minimal example 2:

try:e=Exception()raiseefromeexceptExceptionase:raisee

Identified Cause

Self-references are not checked while unwinding the chained exceptionon line 216 of result.py

Your environment

• CPython versions tested on: 3.9, 3.10
• Operating system and architecture: macOS

Linked PRs

• gh-98458: unittest: bugfix for infinite loop while handling chained exceptions that contain cycles #98459
• [3.11] gh-98458: unittest: bugfix for infinite loop while handling chained exceptions that contain cycles (GH-98459) #99995
• [3.10] gh-98458: unittest: bugfix for infinite loop while handling chained exceptions that contain cycles (GH-98459) #99996