write some tests to check new MarkingDefinition constraints

stix2/test/v21/test_marking_definition.py

@@ -1,7 +1,7 @@
 
 import pytest
 
-from stix2 import exceptions
+from stix2 import exceptions, parse
 from stix2.v21 import (
     TLP_AMBER, TLP_GREEN, TLP_RED, TLP_WHITE, MarkingDefinition, TLPMarking,
 )
@@ -143,3 +143,29 @@ def test_unknown_tlp_marking():
             definition_type='tlp',
             definition=TLPMarking(tlp='gray'),
         )
+
+
+def test_marking_definition_missing_definition():
+    my_favorite_marking = {
+        'type': 'marking-definition',
+        'spec_version': '2.1',
+        'id': 'marking-definition--f9dbe89c-0030-4a9d-8b78-0dcd0a0de874',
+        'name': 'This is the name of my favorite Marking',
+        'definition_type': 'foobar'
+    }
+    with pytest.raises(exceptions.PropertyPresenceError):
+        parse(my_favorite_marking)
+
+
+def test_marking_definition_missing_definition_type():
+    my_favorite_marking = {
+        'type': 'marking-definition',
+        'spec_version': '2.1',
+        'id': 'marking-definition--f9dbe89c-0030-4a9d-8b78-0dcd0a0de874',
+        'name': 'This is the name of my favorite Marking',
+        'definition': {
+            'some_type': 'foobar'
+        }
+    }
+    with pytest.raises(exceptions.InvalidValueError):
+        parse(my_favorite_marking)

stix2/v21/common.py

@@ -226,16 +226,11 @@ class MarkingDefinition(_STIXBase21, _MarkingsMixin):
         definition = self.get("definition")
         definition_type = self.get("definition_type")
         extensions = self.get("extensions")
-        if not extensions and not definition:
+
+        if not (definition_type and definition) and not extensions:
             raise PropertyPresenceError(
-                "MarkingDefinition objects must have the property 'definition' "
-                "if 'extensions' is not present",
-                MarkingDefinition,
-            )
-        if not extensions and not definition_type:
-            raise PropertyPresenceError(
-                "MarkingDefinition objects must have the property 'definition_type' "
-                "if 'extensions' is not present",
+                "MarkingDefinition objects must have the properties "
+                "'definition_type' and 'definition' if 'extensions' is not present",
                 MarkingDefinition,
             )