class_docstr: Unit tests for SEVIRI netCDF reader.
class_docstr_tok: ["Unit","tests","for","SEVIRI","netCDF","reader","."]
docstr: Create a mocked file handler.
docstr_tok: ["Create","a","mocked","file","handler","."]
code: def file_handler(self, counts, h5netcdf):
      """Create a mocked file handler."""
      with mock.patch(
          "satpy.readers.seviri_l1b_nc.open_dataset",
          return_value=self._get_fake_dataset(
              counts=counts, h5netcdf=h5netcdf
          ),
      ):
          return NCSEVIRIFileHandler(
              "filename",
              {
                  "platform_shortname": "MSG3",
                  "start_time": self.scan_time,
                  "service": "MSG",
              },
              {"filetype": "info"},
          )
  
imports: from datetime import datetime
  from unittest import mock
  import numpy
  import pytest
  import xarray
  from satpy.readers.seviri_l1b_nc import NCSEVIRIFileHandler
  from satpy.tests.reader_tests.test_seviri_base import ORBIT_POLYNOMIALS
  from satpy.tests.reader_tests.test_seviri_l1b_calibration import TestFileHandlerCalibrationBase
  from satpy.tests.utils import assert_attrs_equal, make_dataid
label_desc: Use image node_id 3 for calling the TestNCSEVIRIFileHandler obj's underlying member method code with example usage: obj.file_handler(counts, h5netcdf) and returns: NCSEVIRIFileHandler