Fix test_ancillary_variables for CF writer

satpy/tests/writer_tests/test_cf.py

@@ -139,13 +139,14 @@ def test_ancillary_variables(self):
         """Test ancillary_variables cited each other."""
         import xarray as xr
         from satpy import Scene
+        from satpy.tests.utils import make_dataid
         scn = Scene()
         start_time = datetime(2018, 5, 30, 10, 0)
         end_time = datetime(2018, 5, 30, 10, 15)
         da = xr.DataArray([1, 2, 3],
                           attrs=dict(start_time=start_time,
                           end_time=end_time,
-                          prerequisites=[DatasetID('hej')]))
+                          prerequisites=[make_dataid(name='hej')]))
         scn['test-array-1'] = da
         scn['test-array-2'] = da.copy()
         scn['test-array-1'].attrs['ancillary_variables'] = [scn['test-array-2']]
@@ -990,7 +991,7 @@ def test_load_module_with_old_pyproj(self):
             importlib.reload(sys.modules['satpy.writers.cf_writer'])
 
     def test_global_attr_default_history_and_Conventions(self):
-        """Test saving global attributes history and Conventions"""
+        """Test saving global attributes history and Conventions."""
         from satpy import Scene
         import xarray as xr
         scn = Scene()
@@ -1008,7 +1009,7 @@ def test_global_attr_default_history_and_Conventions(self):
                 self.assertIn('Created by pytroll/satpy on', f.attrs['history'])
 
     def test_global_attr_history_and_Conventions(self):
-        """Test saving global attributes history and Conventions"""
+        """Test saving global attributes history and Conventions."""
         from satpy import Scene
         import xarray as xr
         scn = Scene()
@@ -1106,7 +1107,9 @@ def test_collect_datasets_with_latitude_named_lat(self, *mocks):
 
 class EncodingUpdateTest(unittest.TestCase):
     """Test update of netCDF encoding."""
+
     def setUp(self):
+        """Create fake data for testing."""
         import xarray as xr
         self.ds = xr.Dataset({'foo': (('y', 'x'), [[1, 2], [3, 4]]),
                               'bar': (('y', 'x'), [[3, 4], [5, 6]])},
@@ -1115,6 +1118,7 @@ def setUp(self):
                                      'lon': (('y', 'x'), [[7, 8], [9, 10]])})
 
     def test_without_time(self):
+        """Test data without a time dimension."""
         from satpy.writers.cf_writer import update_encoding
 
         # Without time dimension
@@ -1140,6 +1144,7 @@ def test_without_time(self):
                                    'bar': {'chunksizes': (2, 2)}})
 
     def test_with_time(self):
+        """Test data with a time dimension."""
         from satpy.writers.cf_writer import update_encoding
 
         # With time dimension