def setUp(self) -> None:
        """Patch pygac's calibration."""
        super().setUp()

        # Import things to patch here to make them patchable. Otherwise another function
        # might import it first which would prevent a successful patch.
        from pygac.calibration import Calibrator, calibrate_solar, calibrate_thermal
        self.Calibrator = Calibrator
        self.calibrate_thermal = calibrate_thermal
        self.calibrate_thermal.side_effect = fake_calibrate_thermal
        self.calibrate_solar = calibrate_solar
        self.calibrate_solar.side_effect = fake_calibrate_solar