Add missing tests for description requirement

This adds some tests for checking descriptions when the
require_description flag is on for the default model.

tests/test_datamodel.py

@@ -121,7 +121,9 @@ def test_validation(self) -> None:
         with self.assertRaises(ValidationError):
             Column(**units_data)
 
-        # Turn on description requirement for next two tests.
+    def test_require_description(self) -> None:
+        """Test the require_description flag for the `Column` class."""
+        # Turn on description requirement for this test.
         Schema.require_description(True)
 
         # Make sure that setting the flag for description requirement works
@@ -131,14 +133,28 @@ def test_validation(self) -> None:
         # Creating a column without a description when required should throw an
         # error.
         with self.assertRaises(ValidationError):
-            col = Column(
+            Column(
                 **{
                     "name": "testColumn",
                     "@id": "#test_col_id",
                     "datatype": "string",
                 }
             )
 
+        # Creating a column with a None description when required should throw.
+        with self.assertRaises(ValidationError):
+            Column(**{"name": "testColumn", "@id": "#test_col_id", "datatype": "string", "description": None})
+
+        # Creating a column with an empty description when required should
+        # throw.
+        with self.assertRaises(ValidationError):
+            Column(**{"name": "testColumn", "@id": "#test_col_id", "datatype": "string", "description": ""})
+
+        # Creating a column with a description that is not long enough should
+        # throw.
+        with self.assertRaises(ValidationError):
+            Column(**{"name": "testColumn", "@id": "#test_col_id", "datatype": "string", "description": "xy"})
+
         # Turn off flag or it will affect subsequent tests.
         Schema.require_description(False)
 

tests/test_validation.py

@@ -47,6 +47,10 @@ def test_rsp_validation(self) -> None:
         with self.assertRaises(ValidationError):
             RspColumn(name="testColumn", id="#test_col_id", datatype="string", description=None)
 
+        # A column description which is not long enough should throw.
+        with self.assertRaises(ValidationError):
+            RspColumn(name="testColumn", id="#test_col_id", datatype="string", description="xy")
+
         # Creating a valid RSP column should not throw an exception.
         col = RspColumn(
             **{