Could not find platform independent libraries <prefix> when debugging tests in VS Code

I'm trying to write a plugin for QGIS and some tests:

import os
import sys
import unittest

from qgis.core import QgsVectorLayer

class Whatever(unittest.TestCase):
    def test_1(self):
        print(f"PATH: { os.environ["PATH"] }")
        print(f"PYTHONPATH: { os.environ["PYTHONPATH"] }")
        print(f"PYTHONHOME: { os.environ["PYTHONHOME"] }")
        print(f"Executable: { sys.executable }")

        layer = QgsVectorLayer("mylayer")

I also have a launch.json like this one:

{
  "version": "0.2.0",
  "configurations": [
    {
        "name": "Python Debugger: Debug Tests",
        "type": "debugpy",
        "request": "launch",
        "console": "integratedTerminal",
        "purpose": ["debug-test"],
        "cwd": "${workspaceFolder}",
        "envFile": "${workspaceFolder}/.env"
    }
  ]
}

and a settings.json:

{
    "python.defaultInterpreterPath": "C:/OSGeo4W/bin/python.exe",
    "python.analysis.extraPaths": [
        "C:/OSGeo4W/apps/qgis-ltr/python"
    ],
    "python.analysis.autoImportCompletions": true,
    "python.autoComplete.extraPaths": ["C:/OSGeo4W/apps/qgis-ltr/python"],
    "python.testing.unittestArgs": [
        "-v",
        "-s",
        "tests/",
        "-p",
        "*test.py"
    ],
    "python.testing.pytestEnabled": false,
    "python.testing.unittestEnabled": true
}

and finally my .env-file:

PYTHONHOME=C:/OSGeo4W/apps/Python312
PYTHONPATH=C:/OSGeo4W/apps/qgis-ltr/python
PATH=C:/OSGeo4W/apps/qgis-ltr/bin;C:/OSGeo4W/apps/qt5/bin;C:/OSGeo4W/apps/Python312/Scripts;C:/OSGeo4W/bin;C:/Windows/system32;C:/Windows;C:/Windows/system32/WBem
GDAL_DATA=C:/OSGEO4W/share/gdal
GDAL_DRIVER_PATH=C:/OSGEO4W/bin/gdalplugins
GDAL_FILENAME_IS_UTF8=YES
GS_LIB=C:/OSGeo4W/apps/gs/lib
GEOTIFF_CSV=C:/OSGEO4W/share/epsg_csv
O4W_QT_BINARIES=C:/OSGEO4W/apps/Qt5/bin
O4W_QT_DOC=C:/OSGEO4W/apps/Qt5/doc
O4W_QT_HEADERS=C:/OSGEO4W/apps/Qt5/include
O4W_QT_LIBRARIES=C:/OSGEO4W/apps/Qt5/lib
O4W_QT_PLUGINS=C:/OSGEO4W/apps/Qt5/plugins
O4W_QT_PREFIX=C:/OSGEO4W/apps/Qt5
O4W_QT_TRANSLATIONS=C:/OSGEO4W/apps/Qt5/translations
OSGEO4W_ROOT=C:/OSGeo4W
QT_PLUGIN_PATH=C:/OSGEO4W/apps/qgis-ltr/qtplugins
QT_QPA_PLATFORM=windows:altgr
QGIS_PREFIX_PATH=C:/OSGEO4W/apps/qgis
QGIS_PLUGINPATH=D:/git/QgisPlugIns

When I click on the gutter within the test-explorer to debug the above test, I get the forementioned error. However when I just run the test, everything works fine. I already duplictaed the variables from the env-file to the launch.json-file without any success.

I also tried to put these variables into the settings.json-file into the "terminal.integrated.env.windows-section and started a python-interpreter in the terminal. I wrote this script:

from qgis.core import QgsVectorLayer

and it worked. So afterall I can confirm the above paths are 100% correct. However I cannot make it to have them work in both Test-Explorer and in the Terminal. Having them in env-file only makes terminal break ("ImportError: DLL load failed while importing _core: The specified module could not be found". This error relates to the QgsVectorLayer-import-statement), having them in the settings.json only makes test-explorer break. Having them in both leads to "Invalid message: Found duplicate in "env": PATH".

This is my VS Code version:

Version: 1.106.3
Commit: bf9252a2fb45be6893dd8870c0bf37e2e1766d61
Date: 2025-11-25T22:28:18.024Z
Electron: 37.7.0
ElectronBuildId: 12781156
Chromium: 138.0.7204.251
Node.js: 22.20.0
V8: 13.8.258.32-electron.0
OS: Windows_NT x64 10.0.26100

Riproduci il problema usando i file launch.json, settings.json e .env forniti con VS Code Test Explorer, confrontando gli ambienti dei test in debug e normali. Inizia tracciando come vengono assemblate le variabili d’ambiente per gli avvii dei test in debug; il lavoro è completato quando il test viene eseguito in debug con l’ambiente Python di QGIS e le normali esecuzioni dei test e gli import nel terminale continuano a funzionare senza voci duplicate in PATH.