“Singleton” factories, ok or bad?

Question

I\'ve a lot of (abstract) factories and they\'re usually implemented as singletons.

Usually for the convenience of not having to pass them through layers who really hav

Answer 1

I would advise against it, because it makes it very hard to write decent unit tests for the code that calls these factories.

Misko Hevery has a nice article about this on his blog.