I think the best test for a Junior is to ask them to submit some of their OSS or personal fun projects they've worked on. From my perspective, especially with Juniors who aren't expected to be extremely knowledgeable, displaying a sense of curiosity and a willingness to learn is much more important.
If, hypothetically, there's two candidates, one who is more knowledgeable but has no personal projects versus someone who has less knowledge but has worked on different side projects in various languages/domains, I'm always going to pick the latter candidate since they clearly have a passion, and that passion will drive them to pick up the knowledge more than someone who's just doing it for a paycheck and could care less about expanding their own knowledge.
To go one step forward, you can ask them to go into detail about their side project, interesting problems they faced, how they overcame them, etc. Even introverts who are generally worse at small talk are on a much more balanced playing field when talking about something they're passionate about.
Most engineers, including good ones, that I've interviewed have no interesting GitHub contributions. GitHub is also game-able. Bootcamps, in particular, push their graduates to build an interesting GitHub portfolio.
I've found that talking through projects is a weak indicator of competence. It's much easier to memorize talking points than to produce working code.
It may be a result of personal preference, but I struggle to see how talking through challenges encountered with a personal project are a poor indicator of competence. If you ask some boilerplate list of questions, sure, but few if any candidates could memorize all of the random in-the-weeds architecture questions one could ask while talking through someone's project. For a junior specifically, even a non-answer to these questions provides valuable insight into their humility and self-awareness. I also think that it'd be pretty easy to visually weed out personal projects created for the sake of saying one has personal projects, like a bootcamp may push to create, versus an actual passion project, and even easier to weed out during any actual discussion. I suppose YMMV, but in my experience, the body language and flow of discussion are vastly different when someone is passionate about a subject versus not.
Most of this isn't even necessary; just look for passion and <anything> that gets them excited from a relevant technology area, then probe for legitimacy and learn about their interests. Being a jr. is all about the individual learning and skilling up, you really shouldn't be looking for existing expertise.
If, hypothetically, there's two candidates, one who is more knowledgeable but has no personal projects versus someone who has less knowledge but has worked on different side projects in various languages/domains, I'm always going to pick the latter candidate since they clearly have a passion, and that passion will drive them to pick up the knowledge more than someone who's just doing it for a paycheck and could care less about expanding their own knowledge.
To go one step forward, you can ask them to go into detail about their side project, interesting problems they faced, how they overcame them, etc. Even introverts who are generally worse at small talk are on a much more balanced playing field when talking about something they're passionate about.