How does Core Data optional attribute of entity work?

I’m trying to set an entity attribute to be not null by setting it to be none-optional.

But when I assign the attribute nil in test case, it reports no error or exception and the test succeeded. And by the way, how can I make sure this attribute is not optional with unit testing?

Baby *baby = [self.babyModel createWithName:nil];
XCTAssertNil(baby.name);

And when I check the schema of the table in sqlite, it doesn’t set it to be not null. Does that mean this constraint is guaranteed by core data stack instead of sqlite?