Long startup time when running a test from the suite #25827

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2. eleanorjboyd commented on Mar 3, 2026

   

   Eleanor Boyd (eleanorjboyd)

   on Mar 3, 2026

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   Do you have multiple interpreters in one workspace (like separate python projects for different tests)? How many tests are you trying to run and are there any other pytest plugins you are using?
3. Eleanor Boyd (eleanorjboyd)

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   on Mar 3, 2026
4. Eleanor Boyd (eleanorjboyd)

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5. afNewtwen commented on Mar 4, 2026

   

   afNewtwen

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   Do you have multiple interpreters in one workspace (like separate python projects for different tests)? How many tests are you trying to run and are there any other pytest plugins you are using?

   No, I have just one interpreter (from pixi) for the test suite. I am trying to run one test, i am not using any other plugins for pytest.
   The problem seems more severe when trying to debug even one single test.
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7. afNewtwen commented on Mar 4, 2026

   

   afNewtwen

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   I think the problem is related to python environment extension with pixi. As I reported also in the repo of python env plugin, trying to install pixi extension solve also this problem of slow test initialization.
8. Anthony Kim (anthonykim1)

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9. harisbal commented on Jul 28, 2026

   

   harisbal (harisbal)

   on Jul 28, 2026

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   I can confirm the root cause for a Pixi-managed environment: the extension resolves test-debug environment variables by shelling out to pixi shell, which launches an interactive nested shell that never returns control on its own. The extension's own 30s timeout then kills it — and it retries once, so the delay is closer to 60s per debug run.

   Log evidence (ms-python.python/Python.log, extension 2026.4.0):

   19:37:41.460  > pixi shell --manifest-path ./pyproject.toml --environment test && echo '<marker>' && python printEnvVariables.py
   19:38:11.465  [error] getActivatedEnvironmentVariables [Error: Command failed: ...pixi shell...   ← exactly 30.0s later
   19:38:11.508  > pixi shell --manifest-path ./pyproject.toml --environment test && ...   (retry)
   19:38:41.510  [error] getActivatedEnvironmentVariables [Error: Command failed: ...        ← another 30.0s
   19:38:49.244  Test run cancelled
   

   This only happens through the Test Explorer's debug flow — regular launch.json debug configs (which don't force a custom python env-activation lookup) stay fast (<1s) in the same session, and pixi run pytest from a terminal is unaffected since it never goes through this code path.

   Confirmed in the bundled extension source (out/client/extension.js) that the Pixi activation command is built as:

   n=[n.pixi.command..., "shell", "--manifest-path", ..., "--environment", ...]

   i.e. pixi shell, whereas Pixi ships a purpose-built non-interactive equivalent for exactly this use case:

   $ pixi shell-hook --help
   Print the pixi environment activation script.
   You can source the script to activate the environment without needing pixi itself.
   

   Swapping shell → shell-hook --json (or reusing whatever getRunPythonArgs already does with pixi run) in the activation-variable code path should resolve this without the 30s wait. Same underlying issue as #25804 and #25192, just hitting the test-debug path here instead of Jupyter/terminal.

   Workaround in the meantime: add a launch.json config that runs pytest via module: "pytest" directly (bypassing Test Explorer's debug entrypoint) — this uses the same fast path as any other launch.json debug config.