[tasubotadas]

>What does dependency injection give you that a simple combination of Singletons, Constructors, and Factories doesn't?

You don't need to create a "simple combination" of Singletons, Constructors, and Factories.

[BobbyJo]

Don't you? In Java I still had to create the Singleton/Constructor/Factory etc. and register it with the framework as a provider of that type.