Add test to check if data returned by get_dataset is a dask array

satpy/tests/reader_tests/test_virr_l1b.py

@@ -124,10 +124,12 @@ def _fy3_helper(self, platform_name, reader, Emissive_units):
                        'E1': 496.542155, 'E2': 297.444511, 'E3': 288.956557, 'solar_zenith_angle': .1,
                        'satellite_zenith_angle': .1, 'solar_azimuth_angle': .1, 'satellite_azimuth_angle': .1,
                        'longitude': 10}
-        datasets = reader.load([band for band, val in band_values.items()])
+        datasets = reader.load([band for band in band_values])
         for dataset in datasets:
+            # Object returned by get_dataset.
             ds = datasets[dataset.name]
             attributes = ds.attrs
+            self.assertTrue(isinstance(ds.data, da.Array))
             self.assertEqual('VIRR', attributes['sensor'])
             self.assertEqual(platform_name, attributes['platform_name'])
             self.assertEqual(datetime.datetime(2018, 12, 25, 21, 41, 47, 90000), attributes['start_time'])
@@ -166,7 +168,7 @@ def test_fy3b_file(self):
         self.assertTrue(FY3B_reader.file_handlers)
         self._fy3_helper('FY3B', FY3B_reader, 'milliWstts/m^2/cm^(-1)/steradian')
 
-    def test_FY3C_file(self):
+    def test_fy3c_file(self):
         from satpy.readers import load_reader
         FY3C_reader = load_reader(self.reader_configs)
         FY3C_files = FY3C_reader.select_files_from_pathnames(['tf2018359143912.FY3C-L_VIRRX_GEOXX.HDF',