def METHOD_NAME(self):
    # Check a warning is issued when loading a land masked field
    # without a land mask.
    with mock.patch("warnings.warn") as warn:
        list(pp._interpret_fields([self.pp_field]))
    self.assertEqual(warn.call_count, 1)
    warn_msg = warn.call_args[0][0]
    self.assertTrue(
        warn_msg.startswith(
            "Landmask compressed fields " "existed without a landmask"
        ),
        "Unexpected warning message: {!r}".format(warn_msg),
    )