def METHOD_NAME(thetao_cubes):
    """Test ``fix_metadata`` for ``thetao``."""
    vardef = get_var_info('CMIP6', 'Omon', 'thetao')
    fix = Omon(vardef)
    out_cubes = fix.fix_metadata(thetao_cubes)
    assert out_cubes is thetao_cubes
    assert len(out_cubes) == 1
    out_cube = out_cubes[0]
    # Check metadata of depth coordinate
    depth_coord = out_cube.coord('depth')
    assert depth_coord.standard_name == 'depth'
    assert depth_coord.var_name == 'lev'
    assert depth_coord.long_name == 'ocean depth coordinate'
    assert depth_coord.units == 'm'
    assert depth_coord.attributes == {'positive': 'down'}