When you add a programmer to a project with a large code base, what is the best way to get them involved right away? Do you give them formal training in the code base or let them figure it out themselves? What tasks are best to get them up to speed? What kind of tasks are "safe" until they are familiar enough with the project to contribute to it with a full understanding of what they're doing? How do you determine if they've reached a level of full understanding?
The project isn't behind a deadline. I work alone and want to add employees soon. I'd like to know how best to familiarize them with the code base.