class_docstr: Tests for getting the dataset.
class_docstr_tok: ["Tests","for","getting","the","dataset","."]
docstr: Create a file handler for testing.
docstr_tok: ["Create","a","file","handler","for","testing","."]
code: def file_handler(self):
      """Create a file handler for testing."""
      trailer = {
          "15TRAILER": {
              "ImageProductionStats": {
                  "ActualScanningSummary": {
                      "ForwardScanStart": datetime(
                          2006, 1, 1, 12, 15, 9, 304888
                      ),
                      "ForwardScanEnd": datetime(
                          2006, 1, 1, 12, 27, 9, 304888
                      ),
                      "ReducedScan": 0,
                  }
              }
          }
      }
      mda = {
          "channel_list": ["VIS006", "IR_108"],
          "number_of_lines": 4,
          "number_of_columns": 4,
          "is_full_disk": True,
          "platform_name": "MSG-3",
          "offset_corrected": True,
          "projection_parameters": {
              "ssp_longitude": 0.0,
              "h": 35785831.0,
              "a": 6378169.0,
              "b": 6356583.8,
          },
      }
      header = self._fake_header()
      data = self._fake_data()
      with mock.patch(
          "satpy.readers.seviri_l1b_native.NativeMSGFileHandler.__init__",
          return_value=None,
      ):
          fh = NativeMSGFileHandler(
              filename=None, filename_info={}, filetype_info=None
          )
          fh.header = header
          fh.trailer = trailer
          fh.mda = mda
          fh.dask_array = da.from_array(data)
          fh.platform_id = 324
          fh.fill_disk = False
          fh.calib_mode = "NOMINAL"
          fh.ext_calib_coefs = {}
          fh.include_raw_metadata = False
          fh.mda_max_array_size = 100
      return fh
  
imports: from __future__ import annotations
  import os
  import unittest
  import warnings
  from datetime import datetime
  from unittest import mock
  import dask.array
  import numpy
  import pytest
  import xarray
  from satpy.readers.eum_base import recarray2dict, time_cds_short
  from satpy.readers.seviri_l1b_native import ASCII_STARTSWITH, ImageBoundaries, NativeMSGFileHandler, Padder, get_available_channels, has_archive_header
  from satpy.tests.reader_tests.test_seviri_base import ORBIT_POLYNOMIALS, ORBIT_POLYNOMIALS_INVALID
  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 1 for calling the TestNativeMSGDataset obj's underlying member method code with example usage: obj.file_handler() and returns: fh