Add unit test for envreport PYTHONPATH handling

tests/unit/test_venv.py

@@ -1,5 +1,6 @@
 import os
 import sys
+from unittest.mock import MagicMock, patch
 
 import py
 import pytest
@@ -14,6 +15,7 @@
     VirtualEnv,
     getdigest,
     prepend_shebang_interpreter,
+    tox_runenvreport,
     tox_testenv_create,
     tox_testenv_install_deps,
 )
@@ -1233,3 +1235,15 @@ def test_path_change(tmpdir, mocksession, newconfig, monkeypatch):
         path = x.env["PATH"]
         assert os.environ["PATH"] in path
         assert path.endswith(str(venv.envconfig.config.toxinidir) + "/bin")
+
+
+@pytest.mark.parametrize("pythonpath", (None, "blah"))
+@patch("tox.venv.VirtualEnv._get_os_environ")
+def test_runenvreport_pythonpath_discarded(mock_os_environ, pythonpath, newmocksession):
+    mocksession = newmocksession([], "")
+    venv = mocksession.getvenv("python")
+    action = MagicMock()
+    mock_os_environ.return_value = dict(PYTHONPATH=pythonpath) if pythonpath else {}
+    with patch.object(venv, "_pcall") as mock_pcall:
+        tox_runenvreport(venv, action)
+        assert "PYTHONPATH" not in mock_pcall.mock_calls[0].kwargs["env"]