Add test case for using --pythons with nox.options.sessions

tests/test_main.py

@@ -469,6 +469,37 @@ def generate_noxfile(default_session, default_python, alternate_python):
     return generate_noxfile
 
 
+python_current_version = "{}.{}".format(sys.version_info.major, sys.version_info.minor)
+python_next_version = "{}.{}".format(sys.version_info.major, sys.version_info.minor + 1)
+
+
+def test_main_noxfile_options_with_pythons_override(
+    capsys, monkeypatch, generate_noxfile_options_pythons
+):
+    noxfile = generate_noxfile_options_pythons(
+        default_session="test",
+        default_python=python_next_version,
+        alternate_python=python_current_version,
+    )
+
+    monkeypatch.setattr(
+        sys, "argv", ["nox", "--noxfile", noxfile, "--python", python_current_version]
+    )
+
+    with mock.patch("sys.exit") as sys_exit:
+        nox.__main__.main()
+        _, stderr = capsys.readouterr()
+        sys_exit.assert_called_once_with(0)
+
+    for python_version in [python_current_version, python_next_version]:
+        for session in ["test", "launch_rocket"]:
+            line = "Running session {}-{}".format(session, python_version)
+            if session == "test" and python_version == python_current_version:
+                assert line in stderr
+            else:
+                assert line not in stderr
+
+
 @pytest.mark.parametrize(("isatty_value", "expected"), [(True, True), (False, False)])
 def test_main_color_from_isatty(monkeypatch, isatty_value, expected):
     monkeypatch.setattr(sys, "argv", [sys.executable])