catastrophic failure discovering TestCase with short id (e.g. doctests)

[James-E-A]

Type: Bug

Behaviour

Test pane runs no tests and has "Show output to view error logs" message

Steps to reproduce:

1. Create a file foo.py in your workspace:

   #!/usr/bin/env python3
   """
   >>> 2 + 2
   4
   """
   
   # (useless module does nothing, just has a single module-level test)

2. Create a file test_foo.py in your workspace:

   import unittest
   import doctest
   import foo
   
   def load_tests(loader, tests, ignore):
       "https://docs.python.org/3/library/doctest.html#unittest-api"
       tests.addTests(doctest.DocTestSuite(foo))
       return tests

3. Run command, Python: Configure Tests > unittest > . (Root Directory) > test_*.py (4th option); it will create this file .vscode\settings.json in your workspace:

   {
    "python.testing.unittestArgs": [
           "-v",
           "-s",
           ".",
           "-p",
           "test_*.py"
       ],
       "python.testing.pytestEnabled": false,
       "python.testing.unittestEnabled": true
   }

Diagnostic data

Output for Python in the Output panel (View→Output, change the drop-down the upper-right of the Output panel to Python)

2025-08-11 11:45:58.895 [info] Discover tests for workspace name: foo- uri: c:\…\foo
2025-08-11 11:45:59.321 [error] Unittest test discovery error for workspace:  c:\…\foo 
 Traceback (most recent call last):
  File "c:\…\.vscode\extensions\ms-python.python-2025.12.0-win32-x64\python_files\unittestadapter\discovery.py", line 81, in discover_tests
    tests, error = build_test_tree(suite, top_level_dir)  # test tree built successfully here.
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "c:\…\.vscode\extensions\ms-python.python-2025.12.0-win32-x64\python_files\unittestadapter\pvsc_utils.py", line 217, in build_test_tree
    *folders, filename, class_name, function_name = components
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ValueError: not enough values to unpack (expected at least 3, got 1)

Extension version: 2025.10.0
VS Code version: Code 1.101.2 (2901c5ac6db8a986a5666c3af51ff804d05af0d4, 2025-06-24T20:27:15.391Z)
OS version: Windows_NT x64 10.0.22631
Modes:

• Python version (& distribution if applicable, e.g. Anaconda): 7.3.19
• Type of virtual environment used (e.g. conda, venv, virtualenv, etc.): Unknown

System Info

Item	Value
CPUs	11th Gen Intel(R) Core(TM) i5-1145G7 @ 2.60GHz (8 x 1498)
GPU Status	2d_canvas: enabled canvas_oop_rasterization: enabled_on direct_rendering_display_compositor: disabled_off_ok gpu_compositing: enabled multiple_raster_threads: enabled_on opengl: enabled_on rasterization: enabled raw_draw: disabled_off_ok skia_graphite: disabled_off video_decode: enabled video_encode: enabled vulkan: disabled_off webgl: enabled webgl2: enabled webgpu: enabled webnn: disabled_off
Load (avg)	undefined
Memory (System)	15.39GB (3.74GB free)
Process Argv	--crash-reporter-id 82702992-6f5e-40fb-afd0-bb10fcc152ac
Screen Reader	no
VM	0%

A/B Experiments

vsliv368:30146709
binariesv615:30325510
h48ei257:31000450
nativeloc1:31344060
dwcopilot:31170013
bajee813:31263137
6074i472:31201624
dwoutputs:31242946
copilot_t_ci:31333650
e5gg6876:31282496
pythoneinst12:31285622
c7cif404:31314491
996jf627:31283433
pythonrdcb7:31342333
usemplatestapi:31297334
0aa6g176:31307128
747dc170:31275177
aj953862:31281341
pylancequickfixt:31358882
j6a0c355:31346307
convertlamdat:31358880
usemarketplace:31343026
nesew2to5:31336538
agentclaude:31335814
nes-set-on:31340697
63221493:31336333
envsactivate1:31353494
yijiwantestdri0626-t:31336930
0927b901:31350571
f76d9909:31348711
editstats-enabled:31346257

[James-E-A]

I'm not sure why the auto diagnostics tool is claiming Python version 7.3.19. Both py --version and python --version are reporting Python 3.11.9.

[James-E-A]

*The issue still occurs even after switching my project's Python Runtime choice back to the system default. (I don't know why VS Code attached a non-default Python runtime to the project in the first place.)

"python-envs.defaultEnvManager": "ms-python.python:system"

[eleanorjboyd]

hm seems like there is an issue where you testId is not formatted as expected and therefore is throwing an error. Can you run the following for your terminal and let me know the result python -m unittest -v path/to/your/test_file.py. Test file here is whatever file / folder/ workspace you can narrow down the test_id which is causing the issue lives

[James-E-A]

I did not configure any test IDs. Everything needed to reproduce the issue was included in my original ticket, and there is no "test_id" in any of those files.

Running python -m unittest -v foo.py doesn't recognize any tests, but running python -m unittest -v (with no arguments, in the project root) or python -m unittest -v test_foo.py gives successful output.

foo ()
Doctest: foo ... ok

----------------------------------------------------------------------
Ran 1 test in 0.002s

OK

[eleanorjboyd]

thanks for doing this- I don't think I support doctest for unittest at this point, will add this as a feature request then unless you have interest in taking a look at the code and submitting a PR. Thanks

[github-actions]

Thanks for the feature request! We are going to give the community 60 days from when this issue was created to provide 7 👍 upvotes on the opening comment to gauge general interest in this idea. If there's enough upvotes then we will consider this feature request in our future planning. If there's unfortunately not enough upvotes then we will close this issue.

[James-E-A]

If you "don't support" standard unittests that don't fulfill some obscure criteria, the extension should indicate these criteria to the user, instead of its current behavior of vaguely advising the user to gawk at some low-level, completely inactionable catastrophic error messages...