def METHOD_NAME(hdu_index_table):
    """
    This test ensures that the HDUIndexTable works in a case-insensitive
    way concerning the values in the ``HDU_CLASS`` and ``HDU_TYPE`` columns.
    We ended up with this, because initially the HDU index table spec used
    lower-case, but then the ``HDUCLAS`` header keys to all the HDUs
    (e.g. EVENTS, IRFs, ...) were defined in upper-case.
    So for consistency we changed to all upper-case in the spec also for the HDU
    index table, just with a mention that values should be treated in a case-insensitive
    manner for backward compatibility with existing index tables.
    See https://github.com/open-gamma-ray-astro/gamma-astro-data-formats/issues/118
    """
    location = hdu_index_table.hdu_location(obs_id=42, hdu_type="events")
    assert location.path().as_posix() == "a/b"
    location = hdu_index_table.hdu_location(obs_id=42, hdu_type="bkg")
    assert location is None
    assert hdu_index_table.summary().startswith("HDU index table")