test: test get_model_id (doesn't work yet)

Author: kdmccormick

tests/openedx_django_lib/__init__.py

@@ -0,0 +1,42 @@
+"""
+Tests for our django typing utils
+"""
+from typing import NewType, assert_type
+
+from django.db import models
+
+from openedx_django_lib.fields import TypedBigAutoField
+from openedx_django_lib.typing import get_model_id
+
+
+class Foo(models.Model):
+    """
+    A model with a typed ID field
+    """
+    FooID = NewType("FooID", int)
+    type ID = FooID
+
+    class IDField(TypedBigAutoField[ID]):
+        pass
+
+    id = IDField(primary_key=True)
+
+
+def test_get_model_id() -> None:
+    """
+    Test that get_model_id behaves as expected, both at runtime and during typechecking.
+    """
+    foo = Foo()
+
+    # Sanity checks
+    assert_type(foo, Foo)
+    assert_type(foo.id, Foo.ID)
+
+    # get_model_id on a model returns its id
+    assert get_model_id(foo) == foo.id
+    assert_type(get_model_id(foo), Foo.ID)
+
+    # get_model_id on an id returns itself
+    assert get_model_id(foo.id) == foo.id
+    assert_type(get_model_id(foo.id), Foo.ID)
+