Singleton and unit testing

Question

The Effective Java has the following statement on unit testing singletons

Making a class a singleton can make it difficult to test its clients, as it’s im

Answer 1

I think it actually depends on the implementation of the singleton access pattern.

For example

MySingleton.getInstance()

Might be very dificult to test while

MySingletonFactory mySingletonFactory = ...
mySingletonFactory.getInstance() //this returns a MySingleton instance or even a subclass

Doesn't provide any information about the fact that its using a singleton. So you can freely replace your factory.

NOTE: a singleton is defined by being only one instance of that class in an application, however the way it's obtained or stored doesn't have to be through static means.