def setUp(self) -> None:
        """Set up the test case."""
        test_data = np.ones(NUMBER_OF_SCANS, dtype=dtype)
        # Channel 3a
        test_data["id"]["id"][:5] = 891
        # Channel 3b
        test_data["id"]["id"][5:] = 890
        with NamedTemporaryFile(mode='w+', suffix='.hmf', delete=False) as hrpt_file:
            self.filename = hrpt_file.name
            test_data.tofile(hrpt_file)