[pylaterreur]

test_post in tests/integration/test_urllib3.py fails now and then with BrokenPipeError: in my runs, 9 times in 100 on CPython 3.13 and 4 in 100 on 3.14. It's a test bug: since urllib3 2.0, the third positional argument of request() is the body, not the form fields.

	request() signature
urllib3 1.26	request(method, url, fields=None, ...)
urllib3 2.0	request(method, url, body=None, fields=None, ...)

urllib3-future, which the niquests jobs use, has the 2.x signature.

So verify_pool_mgr.request("POST", url, data) sends the dict as the body. urllib3 iterates it and sends its keys as a chunked body, which httpbin answers with a 501 without reading it. The test only compared the recorded and replayed responses, so it kept passing on two identical 501s, except when the server closed the connection while urllib3 was still sending.

Fix

Pass the form as fields=data, as the test meant to, and check that httpbin echoes it, so the test fails if the form stops being sent.

Tests

• test_post (http and https) passes on CPython 3.13.16, 3.14.8 and 3.15.0rc2 with urllib3 2.8.0. It also passes on 3.15.0rc2 with urllib3-future 2.25.901, with and without Fix niquests connection reuse with urllib3-future 2.25.901 #1056.
• I ran test_post 100 times per version, under the same load, in a network namespace like CI's offline step:
  • with master's test, 9 runs failed on 3.13.16 and 4 on 3.14.8;
  • with this change, none did.
• CI on my fork: every job has the same outcome as on unmodified master, and test_post passes in all of them. The failing jobs are the tests-niquests ones, fixed by Fix niquests connection reuse with urllib3-future 2.25.901 #1056, and pypy-3.11, because of a tornado bug on PyPy 8.0. iostream: Release memoryviews explicitly for PyPy 8.0 compatibility tornadoweb/tornado#3750 fixed it, but the fix isn't released yet (see Support Python 3.14 and 3.15, test free-threaded builds in CI #1058).
• pre-commit run --all-files and codespell: clean.

Three other tests fail the same way: test_post_chunked_binary, test_body_consumed_once_iterator and test_body_consumed_once_stream. They send chunked bodies on purpose, so they need pytest-httpbin's server to handle them: kevin1024/pytest-httpbin#101.

🤖 Generated with Claude Code

https://claude.ai/code/session_01GwUvhmzgfkiZ6vo4uGyesN

[cclauss]

@kevin1024 Please approve the GitHub Actions test runs to see if they pass.

[pylaterreur]

@kevin1024 @cclauss Friendly ping: could this be merged, or is anything still needed from my side? Thanks!

[kevin1024]

This has been released in v8.4.0. Thanks @pylaterreur!