def METHOD_NAME(healpix, survey, program, reduxdir):
    """Validate healpix tile worth of spectra."""
    filedir = os.path.join(reduxdir, 'healpix', survey, program, str(healpix//100), str(healpix))
    for prefix in ['coadd', 'redrock']:
        specfile = os.path.join(filedir, '{}-{}-{}-{}.fits'.format(prefix, survey, program, healpix))
        if not os.path.isfile(specfile):
            raise IOError('Missing {}'.format(specfile))