def test_overlay_file_bad_type():
    plot = SigPlot()
    assert plot.inputs == []

    path = 3
    with pytest.raises(TypeError):
        plot.overlay_file(path)
def test_overlay_file_non_empty():
    plot = SigPlot()
    assert plot.inputs == []

    path = "foo.tmp"
    plot.overlay_file(path)
    assert plot.inputs == [path]