class_docstr: Test the HRITFileHandler.
class_docstr_tok: ["Test","the","HRITFileHandler","."]
docstr: Test reading the hrv band.
docstr_tok: ["Test","reading","the","hrv","band","."]
code: def test_read_hrv_band(self, memmap):
      """Test reading the hrv band."""
      nbits = self.reader.mda["number_of_bits_per_pixel"]
      memmap.return_value = np.random.randint(
          0, 256, size=int((464 * 5568 * nbits) / 8), dtype=np.uint8
      )
      res = self.reader.read_band("HRV", None)
      assert res.shape == (464, 5568)
  
imports: import unittest
  from datetime import datetime
  from unittest import mock
  import numpy
  import pytest
  import xarray
  from numpy import testing
  from pyproj import CRS
  import satpy.tests.reader_tests.test_seviri_l1b_hrit_setup
  from satpy.readers.seviri_l1b_hrit import HRITMSGEpilogueFileHandler, HRITMSGFileHandler, HRITMSGPrologueFileHandler
  from satpy.tests.reader_tests.test_seviri_base import 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 2 for calling the TestHRITMSGFileHandlerHRV obj's underlying member method code with example usage: obj.test_read_hrv_band(memmap) without return types