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

Reproduce the failure using the provided launch.json, settings.json, and .env with the VS Code Test Explorer, comparing the debug and normal test environments. Start by tracing how environment variables are assembled for debug-test launches; done means the test debugs with the QGIS Python environment while normal test runs and terminal imports continue to work without duplicate PATH entries.