Tests are used in schools because it is the only way that a teacher can keep up with what a whole classroom (or six or eight classrooms) of students are doing. It's really not needed with homeschooling. Don't let yourself fall into the trap of taking a system of education that is designed for working with whole classrooms full of children and trying to use it with one child.
Keeping a notebook of unfamiliar vocabulary words seems reasonable. Why not review that list with him each day and then pick a word together to "adopt" into your vocabulary? Make it almost a game to see how many excuses you can find to use that word over that day, or the next few days? Unless your state law requires you to do so, why give assignments that can be passed/failed at all? I'd suggest looking for ways to "improve" instead.
Obviously, he'll need to do some "formal" exercises. He'll need to be able to write well, for example. Perhaps he could practice this in non-traditional ways, though. Perhaps a blog where you review posts before he "publishes" them. This way he is also learning technology.