def METHOD_NAME(
    mock_sub,
    capsys,
    creationflags,
    final_creationflags,
):
    """Creationflags used to simulate start_new_session=True should be merged with any
    existing flags."""
    mock_sub.tools.host_os = "Windows"
    # use commented test below when merging creationflags is allowed
    with pytest.raises(
        AssertionError, match="Subprocess called with creationflags set"
    ):
        mock_sub.run(
            ["hello", "world"],
            start_new_session=True,
            creationflags=creationflags,
            stream_output=False,
        )