We could simply add a getTemplate() method, but then we'd be adding methods to the public interface solely to allow testing, which is not a good approach. It s

We could simply add a getTemplate() method, but then we'd be adding methods to the public interface solely to allow testing, which is not a good approach. It seems like his solution does this anyway by exposing the supplant function. Despite the underscore, it's not private; it's that brand of smile-and-a-wink private popular in python. I'm not a big fan of that. I like to keep the interface simple for consumers of the class, and even if I know to ignore underscored members, it's still noise. That said, I don't have a better solution. Maybe the trade-off is worth it for well-tested software. I suppose you could structure your code so that objects can respond to some debug or test flag that forces them to expose their internals, but that might be a lot of work for little benefit. At the end of the day, maybe it's best to call this "good enough" and get back to work.