fix dash test runner

tests/test_tracker_test_runner.py

@@ -6,6 +6,7 @@ constructed without an explicit ``repo_root``.
 """
 
 import json
+import sys
 import time
 import urllib.error
 import urllib.request
@@ -16,7 +17,7 @@ import pytest
 from meshnet_tracker.accounts import AccountStore
 from meshnet_tracker.server import TrackerServer
 from meshnet_tracker.test_runner import TestRunManager as RunManager
-from meshnet_tracker.test_runner import discover_repo_root
+from meshnet_tracker.test_runner import _test_python, discover_repo_root
 
 
 def _make_repo(tmp_path: Path) -> Path:
@@ -119,6 +120,16 @@ def test_enable_flag_constructs_runner_against_real_repo(monkeypatch):
     assert (tracker._test_runner.repo_root / "tests" / "conftest.py").is_file()
 
 
+def test_runner_uses_configured_project_python(monkeypatch, tmp_path):
+    python = tmp_path / "python"
+    python.touch(mode=0o755)
+    monkeypatch.setenv("MESHNET_PYTHON", str(python))
+    assert _test_python() == str(python)
+
+    monkeypatch.setenv("MESHNET_PYTHON", str(tmp_path / "missing-python"))
+    assert _test_python() == sys.executable
+
+
 def test_collection_lists_tests_and_excludes_real_inference(tmp_path, monkeypatch):
     monkeypatch.delenv("MESHNET_ENABLE_REAL_INFERENCE_TESTS", raising=False)
     tracker, port, admin, _user = _start_tracker(tmp_path)