[Flaky test] MCOREFS 1.4 is flaky

[andy31415]

This test seems VERY flaky. a recent example:

https://github.com/project-chip/connectedhomeip/actions/runs/25434905164/job/74613016183?pr=71912

...

[2026-05-06 13:03:23.989505][TEST][STDOUT][MatterTest] 05-06 13:03:23.988 INFO >>> [E:55539i S:12259 M:187860326 (Ack:96663665)] (S) Msg RX from 1:0000000012344321 [EF6B] to 000000000001B669 --- Type 0001:05 (IM:ReportData) (B:72)
[2026-05-06 13:03:23.992817][TEST][STDOUT][MatterTest] 05-06 13:03:23.990 INFO Endpoints on DUT_FSA_BRIDGE: old={1}, new={1}
[2026-05-06 13:03:23.994244][TEST][STDOUT][MatterTest] 05-06 13:03:23.990 ERROR Exception occurred in test_TC_MCORE_FS_1_4.
[2026-05-06 13:03:23.994269][TEST][STDOUT]Traceback (most recent call last):
[2026-05-06 13:03:23.994335][TEST][STDOUT]  File "/__w/connectedhomeip/connectedhomeip/out/venv/lib/python3.12/site-packages/mobly/base_test.py", line 801, in exec_one_test
[2026-05-06 13:03:23.994346][TEST][STDOUT]    test_method()
[2026-05-06 13:03:23.994415][TEST][STDOUT]  File "/__w/connectedhomeip/connectedhomeip/out/venv/lib/python3.12/site-packages/matter/testing/decorators.py", line 266, in async_runner
[2026-05-06 13:03:23.994442][TEST][STDOUT]    return _async_runner(body, self, *args, **kwargs)
[2026-05-06 13:03:23.994470][TEST][STDOUT]           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[2026-05-06 13:03:23.994539][TEST][STDOUT]  File "/__w/connectedhomeip/connectedhomeip/out/venv/lib/python3.12/site-packages/matter/testing/decorators.py", line 253, in _async_runner
[2026-05-06 13:03:23.994602][TEST][STDOUT]    return test_instance.event_loop.run_until_complete(asyncio.wait_for(body(test_instance, *args, **kwargs), timeout=timeout))
[2026-05-06 13:03:23.994665][TEST][STDOUT]           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[2026-05-06 13:03:23.994708][TEST][STDOUT]  File "/usr/lib/python3.12/asyncio/base_events.py", line 687, in run_until_complete
[2026-05-06 13:03:23.994722][TEST][STDOUT]    return future.result()
[2026-05-06 13:03:23.994737][TEST][STDOUT]           ^^^^^^^^^^^^^^^
[2026-05-06 13:03:23.994771][TEST][STDOUT]  File "/usr/lib/python3.12/asyncio/tasks.py", line 520, in wait_for
[2026-05-06 13:03:23.994783][TEST][STDOUT]    return await fut
[2026-05-06 13:03:23.994794][TEST][STDOUT]           ^^^^^^^^^
[2026-05-06 13:03:23.994853][TEST][STDOUT]  File "/__w/connectedhomeip/connectedhomeip/src/python_testing/TC_MCORE_FS_1_4.py", line 405, in test_TC_MCORE_FS_1_4
[2026-05-06 13:03:23.994904][TEST][STDOUT]    asserts.assert_equal(len(unique_endpoints_set), 1, "Expected exactly one new endpoint on DUT_FSA")
[2026-05-06 13:03:23.994971][TEST][STDOUT]  File "/__w/connectedhomeip/connectedhomeip/out/venv/lib/python3.12/site-packages/mobly/asserts.py", line 66, in assert_equal
[2026-05-06 13:03:23.994987][TEST][STDOUT]    _call_unittest_assertion(
[2026-05-06 13:03:23.995060][TEST][STDOUT]  File "/__w/connectedhomeip/connectedhomeip/out/venv/lib/python3.12/site-packages/mobly/asserts.py", line 50, in _call_unittest_assertion
[2026-05-06 13:03:23.995087][TEST][STDOUT]    raise signals.TestFailure(my_msg, extras=extras)
[2026-05-06 13:03:23.995136][TEST][STDOUT]mobly.signals.TestFailure: Details=0 != 1 Expected exactly one new endpoint on DUT_FSA, Extras=None
[2026-05-06 13:03:23.995298][TEST][STDOUT][MatterTest] 05-06 13:03:23.992 INFO <<< [E:55539i S:12259 M:96663666 (Ack:187860326)] (S) Msg TX from 000000000001B669 to 1:0000000012344321 [EF6B] [UDP:[fe80::8d4:26ff:feac:7192%veth0]:5540] --- Type 0000:10 (SecureChannel:StandaloneAck) (B:34)
[2026-05-06 13:03:23.996054][TEST][STDOUT][MatterTest] 05-06 13:03:23.996 INFO 		***** Test Failure : 
[2026-05-06 13:03:23.996130][TEST][STDOUT][MatterTest] 05-06 13:03:23.996 INFO Finished test in 11310277.0ms
[2026-05-06 13:03:23.996294][TEST][STDOUT][MatterTest] 05-06 13:03:23.996 ERROR 
[2026-05-06 13:03:23.996299][TEST][STDOUT]
[2026-05-06 13:03:23.996333][TEST][STDOUT]******************************************************************
[2026-05-06 13:03:23.996336][TEST][STDOUT]*
[2026-05-06 13:03:23.996367][TEST][STDOUT]* Test test_TC_MCORE_FS_1_4 failed for the following reason:
[2026-05-06 13:03:23.996404][TEST][STDOUT]* Details=0 != 1 Expected exactly one new endpoint on DUT_FSA, Extras=None
[2026-05-06 13:03:23.996407][TEST][STDOUT]*
[2026-05-06 13:03:23.996465][TEST][STDOUT]* File "/__w/connectedhomeip/connectedhomeip/src/python_testing/TC_MCORE_FS_1_4.py", line 405, in test_TC_MCORE_FS_1_4
[2026-05-06 13:03:23.996515][TEST][STDOUT]* asserts.assert_equal(len(unique_endpoints_set), 1, "Expected exactly one new endpoint on DUT_FSA")
[2026-05-06 13:03:23.996518][TEST][STDOUT]*
[2026-05-06 13:03:23.996525][TEST][STDOUT]* Test step:
[2026-05-06 13:03:23.996611][TEST][STDOUT]*     6: DUT_FSA synchronizes TH_SERVER_NO_UID onto DUT_FSA's fabric and copies the UniqueID presented by TH_FSA's Bridged Device Basic Information Cluster.	Expected outcome: 
[2026-05-06 13:03:23.996614][TEST][STDOUT]*
[2026-05-06 13:03:23.996624][TEST][STDOUT]* Endpoint: None
[2026-05-06 13:03:23.996626][TEST][STDOUT]*
[2026-05-06 13:03:23.996660][TEST][STDOUT]*******************************************************************
```

[andy31415]

ci_logs_for_failed_mcorefs_1_4.txt

Here is the full CI log for the failure

[andy31415]

mcorefs_1_4_fail_example_2.txt

Another CI log for failure, this time from a master run

[andy31415]

mcorefs_1_4_fail_example_3.txt

Another example from a recent master run.
Generally this seems to fail about 10-20% of the time.

https://project-chip.github.io/connectedhomeip/allure-report/ci_tests/138856/index.html says 93% pass rate: