[CERT-TEST-FAILURE] IDM-3-2 fails with script issue on step 3

[Shadi-Silabs]

Feature Area

Other

Test Case

TC-IDM-3-2

Reproduction steps

During Matter 1.6/ TE2
IDM-3-2 step3: TH sends the WriteRequestMessage to the DUT to write an unsupported attribute. DUT responds with the Write Response action

The script chooses ActiveWiredFaults from PowerSource but it fails as below:

PYTHON_TEST | 2026-03-04 19:14:42.318850 | [MatterTest] 03-04 19:14:31.342 ERROR Exception occurred in test_TC_IDM_3_2. PYTHON_TEST | 2026-03-04 19:14:42.321591 | Traceback (most recent call last): PYTHON_TEST | 2026-03-04 19:14:42.322973 | File "/usr/local/lib/python3.12/dist-packages/mobly/base_test.py", line 801, in exec_one_test PYTHON_TEST | 2026-03-04 19:14:42.324218 | test_method() PYTHON_TEST | 2026-03-04 19:14:42.327353 | File "/usr/local/lib/python3.12/dist-packages/matter/testing/decorators.py", line 265, in async_runner PYTHON_TEST | 2026-03-04 19:14:42.328857 | return _async_runner(body, self, *args, **kwargs) PYTHON_TEST | 2026-03-04 19:14:42.330280 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ PYTHON_TEST | 2026-03-04 19:14:42.333305 | File "/usr/local/lib/python3.12/dist-packages/matter/testing/decorators.py", line 253, in _async_runner PYTHON_TEST | 2026-03-04 19:14:42.334804 | return test_instance.event_loop.run_until_complete(asyncio.wait_for(body(test_instance, *args, **kwargs), timeout=timeout)) PYTHON_TEST | 2026-03-04 19:14:42.335922 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ PYTHON_TEST | 2026-03-04 19:14:42.338421 | File "/usr/lib/python3.12/asyncio/base_events.py", line 687, in run_until_complete PYTHON_TEST | 2026-03-04 19:14:42.339601 | return future.result() PYTHON_TEST | 2026-03-04 19:14:42.340699 | ^^^^^^^^^^^^^^^ PYTHON_TEST | 2026-03-04 19:14:42.343167 | File "/usr/lib/python3.12/asyncio/tasks.py", line 520, in wait_for PYTHON_TEST | 2026-03-04 19:14:42.344395 | return await fut PYTHON_TEST | 2026-03-04 19:14:42.345771 | ^^^^^^^^^ PYTHON_TEST | 2026-03-04 19:14:42.347023 | File "/root/python_testing/scripts/sdk/TC_IDM_3_2.py", line 178, in test_TC_IDM_3_2 PYTHON_TEST | 2026-03-04 19:14:42.350434 | write_status2 = await self.write_single_attribute( PYTHON_TEST | 2026-03-04 19:14:42.351886 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ PYTHON_TEST | 2026-03-04 19:14:42.353246 | File "/usr/local/lib/python3.12/dist-packages/matter/testing/matter_testing.py", line 1026, in write_single_attribute PYTHON_TEST | 2026-03-04 19:14:42.356267 | write_result = await dev_ctrl.WriteAttribute(node_id, [(endpoint_id, attribute_value)]) PYTHON_TEST | 2026-03-04 19:14:42.357568 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ PYTHON_TEST | 2026-03-04 19:14:42.358737 | File "/usr/local/lib/python3.12/dist-packages/matter/ChipDeviceCtrl.py", line 1892, in WriteAttribute PYTHON_TEST | 2026-03-04 19:14:42.361590 | return await self._WriteAttribute(nodeId=nodeId, PYTHON_TEST | 2026-03-04 19:14:42.362947 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ PYTHON_TEST | 2026-03-04 19:14:42.364195 | File "/usr/local/lib/python3.12/dist-packages/matter/ChipDeviceCtrl.py", line 1918, in _WriteAttribute PYTHON_TEST | 2026-03-04 19:14:42.367330 | ClusterAttribute.WriteAttributes( PYTHON_TEST | 2026-03-04 19:14:42.368572 | File "/usr/local/lib/python3.12/dist-packages/matter/clusters/Attribute.py", line 1042, in WriteAttributes PYTHON_TEST | 2026-03-04 19:14:42.369841 | pyWriteAttributes, numberOfAttributes = _prepare_write_attributes_data( PYTHON_TEST | 2026-03-04 19:14:42.370941 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ PYTHON_TEST | 2026-03-04 19:14:42.372028 | File "/usr/local/lib/python3.12/dist-packages/matter/clusters/Attribute.py", line 1023, in _prepare_write_attributes_data PYTHON_TEST | 2026-03-04 19:14:42.373143 | tlv = attr.Attribute.ToTLV(None, attr.Data) PYTHON_TEST | 2026-03-04 19:14:42.376372 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ PYTHON_TEST | 2026-03-04 19:14:42.377698 | File "/usr/local/lib/python3.12/dist-packages/matter/clusters/ClusterObjects.py", line 320, in ToTLV PYTHON_TEST | 2026-03-04 19:14:42.378885 | cls.attribute_type.PutFieldToTLV(tag, PYTHON_TEST | 2026-03-04 19:14:42.381964 | File "/usr/local/lib/python3.12/dist-packages/matter/clusters/ClusterObjects.py", line 97, in PutFieldToTLV PYTHON_TEST | 2026-03-04 19:14:42.383415 | self._PutSingleElementToTLV( PYTHON_TEST | 2026-03-04 19:14:42.384707 | File "/usr/local/lib/python3.12/dist-packages/matter/clusters/ClusterObjects.py", line 60, in _PutSingleElementToTLV PYTHON_TEST | 2026-03-04 19:14:42.387657 | if issubclass(elementType, ClusterObject): PYTHON_TEST | 2026-03-04 19:14:42.389100 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ PYTHON_TEST | 2026-03-04 19:14:42.390292 | TypeError: issubclass() arg 1 must be a class PYTHON_TEST | 2026-03-04 19:14:42.393016 | [MatterTest] 03-04 19:14:31.363 ERROR
Full logs can be seen here:

TC-IDM-3-2_EP0_2026_03_04_14_13_39.log

Bug prevalence

every time i run with TH version v2.15-beta2.2+spring2026

GitHub hash of the SDK that was being used

4bf7cfc

Platform

other

Anything else?

No response

[KishokG]

@j-ororke Can you please take a look into this issue? Thanks!

[j-ororke]

@KishokG and @Shadi-Silabs,
A potential fix for the above issue can be found here: #43540
This resolves the TypeError: issubclass() arg 1 must be a class crash in step 3 by iterating through unsupported attribute candidates and skipping any whose Python type cannot be serialized with a simple value, rather than always picking the first one found. Tested locally on a Raspberry Pi in both the TH CLI and UI for TH version v2.15-beta2.2+spring2026.