class_docstr: Test the IciL1bNCFileHandler reader.
class_docstr_tok: ["Test","the","IciL1bNCFileHandler","reader","."]
docstr: Test calibrate brightness temperature.
docstr_tok: ["Test","calibrate","brightness","temperature","."]
code: def test_calibrate_bt(self, reader):
      """Test calibrate brightness temperature."""
      radiance = xr.DataArray(
          np.array(
              [
                  [0.060, 0.065, 0.070, 0.075],
                  [0.080, 0.085, 0.090, 0.095],
              ]
          )
      )
      cw = 6.1145
      a = 1.0
      b = 0.0
      bt = reader._calibrate_bt(radiance, cw, a, b)
      expected_bt = np.array(
          [
              [198.22929022, 214.38700287, 230.54437184, 246.70146465],
              [262.85833223, 279.01501371, 295.17153966, 311.32793429],
          ]
      )
      np.testing.assert_allclose(bt, expected_bt)
  
imports: from datetime import datetime
  from unittest.mock import patch
  import numpy
  import pytest
  import xarray
  from netCDF4 import Dataset
  from satpy.readers.ici_l1b_nc import IciL1bNCFileHandler, InterpolationType
label_desc: Use image node_id 13 for calling the TestIciL1bNCFileHandler obj's underlying member method code with example usage: obj.test_calibrate_bt(reader) without return types