def METHOD_NAME(self, iwsi, save_dataset):
    """Test that a P-mode image is converted to uint8s."""
    nt = pyninjotiff_mock.ninjotiff
    nt.reset_mock()
    from satpy.writers.ninjotiff import NinjoTIFFWriter
    ntw = NinjoTIFFWriter()
    dataset = xr.DataArray([1, 2, 3]).astype(int)
    img = FakeImage(dataset, 'P')
    ntw.save_image(img, filename='bla.tif', compute=False)
    assert nt.save.mock_calls[0][1][0].data.dtype == np.uint8