fix(jambo): Add NullTypeParser implementation and tests (#2)

tests/parser/test_null_type_parser.py

@@ -0,0 +1,43 @@
+from jambo.parser import NullTypeParser
+
+from unittest import TestCase
+
+
+class TestNullTypeParser(TestCase):
+    def test_null_parser_no_options(self):
+        parser = NullTypeParser()
+
+        properties = {"type": "null"}
+
+        type_parsing, type_validator = parser.from_properties_impl(
+            "placeholder", properties
+        )
+
+        self.assertEqual(type_parsing, None)
+        self.assertEqual(type_validator, {"default": None})
+
+    def test_null_parser_with_default(self):
+        parser = NullTypeParser()
+
+        properties = {
+            "type": "null",
+            "default": None,
+        }
+
+        type_parsing, type_validator = parser.from_properties_impl(
+            "placeholder", properties
+        )
+
+        self.assertEqual(type_parsing, None)
+        self.assertEqual(type_validator["default"], None)
+
+    def test_null_parser_with_invalid_default(self):
+        parser = NullTypeParser()
+
+        properties = {
+            "type": "null",
+            "default": "invalid",
+        }
+
+        with self.assertRaises(ValueError):
+            parser.from_properties_impl("placeholder", properties)