Unit testing & assertions example (newbie)

If I get this right, Unit Testing is all about testing if our app
our data the way it should. In other words it’s all about testing the
model? (ex. does our app *rejects product titles with fewer than 10
chars *as
it should?)

So the way to do unit tests are always to use assertions? Or there are
other ways too?

I’m playing with the code from “Agile Development with Rails” where we
create an online store, and this is a test for my product title that I
wrote. Can you tell me if it’s the best way to do it or maybe there’s a
quicker and better solution?

test “title length must be greater than 10” do