[FB] [PI-3474] Add tests for the loading and saving of ancillary vari…

…ables (#3799)

lib/iris/tests/results/netcdf/TestNetCDFSave__ancillaries/flag.cdl

@@ -0,0 +1,46 @@
+dimensions:
+	grid_latitude = 9 ;
+	grid_longitude = 11 ;
+	time = 7 ;
+variables:
+	int64 air_potential_temperature(time, grid_latitude, grid_longitude) ;
+		air_potential_temperature:standard_name = "air_potential_temperature" ;
+		air_potential_temperature:units = "K" ;
+		air_potential_temperature:grid_mapping = "rotated_latitude_longitude" ;
+		air_potential_temperature:coordinates = "air_pressure forecast_period" ;
+		air_potential_temperature:ancillary_variables = "quality_flag" ;
+	int rotated_latitude_longitude ;
+		rotated_latitude_longitude:grid_mapping_name = "rotated_latitude_longitude" ;
+		rotated_latitude_longitude:longitude_of_prime_meridian = 0. ;
+		rotated_latitude_longitude:earth_radius = 6371229. ;
+		rotated_latitude_longitude:grid_north_pole_latitude = 37.5 ;
+		rotated_latitude_longitude:grid_north_pole_longitude = 177.5 ;
+		rotated_latitude_longitude:north_pole_grid_longitude = 0. ;
+	double time(time) ;
+		time:axis = "T" ;
+		time:units = "hours since 1970-01-01 00:00:00" ;
+		time:standard_name = "time" ;
+		time:calendar = "gregorian" ;
+	double grid_latitude(grid_latitude) ;
+		grid_latitude:axis = "Y" ;
+		grid_latitude:units = "degrees" ;
+		grid_latitude:standard_name = "grid_latitude" ;
+	double grid_longitude(grid_longitude) ;
+		grid_longitude:axis = "X" ;
+		grid_longitude:units = "degrees" ;
+		grid_longitude:standard_name = "grid_longitude" ;
+	double air_pressure ;
+		air_pressure:units = "Pa" ;
+		air_pressure:standard_name = "air_pressure" ;
+	double forecast_period(time) ;
+		forecast_period:units = "hours" ;
+		forecast_period:standard_name = "forecast_period" ;
+	byte quality_flag(time, grid_latitude, grid_longitude) ;
+		quality_flag:long_name = "quality_flag" ;
+		quality_flag:flag_meanings = "PASS FAIL MISSING" ;
+		quality_flag:flag_values = 1b, 2b, 9b ;
+
+// global attributes:
+		:source = "Iris test case" ;
+		:Conventions = "CF-1.7" ;
+}

lib/iris/tests/test_netcdf.py

@@ -460,14 +460,21 @@ def test_default_units(self):
             variables:
                 int64 qqv(ayv, axv) ;
                     qqv:long_name = "qq" ;
+                    qqv:ancillary_variables = "my_av" ;
+                    qqv:cell_measures = "area: my_areas" ;
                 int64 ayv(ayv) ;
                     ayv:long_name = "y" ;
                 int64 axv(axv) ;
                     axv:units = "1" ;
                     axv:long_name = "x" ;
+                double my_av(axv) ;
+                    my_av:long_name = "refs" ;
+                double my_areas(ayv, axv) ;
+                    my_areas:long_name = "areas" ;
             data:
                 axv = 11, 12, 13;
                 ayv = 21, 22;
+                my_areas = 110., 120., 130., 221., 231., 241.;
             }
             """
         self.tmpdir = tempfile.mkdtemp()
@@ -485,6 +492,12 @@ def test_default_units(self):
         self.assertEqual(cubes[0].units, as_unit("unknown"))
         self.assertEqual(cubes[0].coord("y").units, as_unit("unknown"))
         self.assertEqual(cubes[0].coord("x").units, as_unit(1))
+        self.assertEqual(
+            cubes[0].ancillary_variable("refs").units, as_unit("unknown")
+        )
+        self.assertEqual(
+            cubes[0].cell_measure("areas").units, as_unit("unknown")
+        )
 
     def test_units(self):
         # Test exercising graceful cube and coordinate units loading.
@@ -1263,6 +1276,21 @@ def test_aliases(self):
             iris.save([testcube_1, testcube_2], filename)
             self.assertCDL(filename)
 
+    def test_flag(self):
+        testcube = stock.realistic_3d()
+        flag = iris.coords.AncillaryVariable(
+            np.ones(testcube.shape, dtype=np.int8),
+            long_name="quality_flag",
+            attributes={
+                "flag_meanings": "PASS FAIL MISSING",
+                "flag_values": np.array([1, 2, 9], dtype=np.int8),
+            },
+        )
+        testcube.add_ancillary_variable(flag, (0, 1, 2))
+        with self.temp_filename(suffix=".nc") as filename:
+            iris.save(testcube, filename)
+            self.assertCDL(filename)
+
 
 class TestNetCDF3SaveInteger(tests.IrisTest):
     def setUp(self):