Adds test code

entities.py

@@ -0,0 +1,14 @@
+from dataclasses import dataclass, field
+
+ENTITY_INDEX = 0
+
+
+def generate_id():
+    global ENTITY_INDEX
+    ENTITY_INDEX += 1
+    return ENTITY_INDEX
+
+
+@dataclass
+class BaseEntity:
+    id: int = field(default_factory=generate_id)

test.py

@@ -0,0 +1,3 @@
+from entities import BaseEntity
+
+object = BaseEntity()