I can agree with the basics of what you're saying, but you can't really hold newbies to the same standard as a professional developer. You have to pick your battles so as not to overwhelm them. Maybe they don't really know how methods work, so everything is kept in the main method until they learn the basics of variables, if statements, and for loops. Proposing unit testing will go over their heads, I think. But encouraging them to break the problem down (is it your input or output? can you hardcode the input and get it working? what are the values of each variable before, during, and after that loop?) is actually teaching the skills that are required for unit testing. You can't require unit testing before teaching the prerequisites of isolating the problem, which we try to teach by asking for an SSCCE.
But like I said this is really a personal preference. If you want to try to ask for unit testing, go for it.