How do the myriad Derby drivers work?

I am using Apache Derby in-memory with no daemon or outside dependencies in support of being called from JUnit tests. This is working pretty well, but what it's going to be doing underneath will eventually cause me to walk the following road, I think.

I am using I find myself needing to register a driver such that a call to
DriverManager.getConnection() will find it. (Or, I think I do; I'm looking at some existing homespun mocking code that does this and I'm trying to imitate then replace it with Derby.)

    DriverManager.registerDriver( new org.apache.derby.jdbc.AutoLoadedDriver() );

Here and there, in examples on-line, I see references to drivers like:

However, unless I'm mistaken, these do not exist in derby I am using derby- I have also tried adding the same version's shared and tools JARs.

Any thoughts on this would help. I only discovered this phenomenon of registering drivers today, so I'm stumbling around a bit.