Yikes, that doesn't sound like a fun way to grade. Sounds about like what I do with students that are competing in ACSL competitions. But that's only 6 or 7 students, 4 times a year. I can't imagine trying it with 100 students all year.
Here's what I'm doing, and what I've done.
This is what I'm doing now. Kids login to Canvas and it launches an LTI tool embedded in an assignment. They do their coding in Chrome and click the Test button when they're ready. They can keep testing until their happy with the grade. Grades get sent back to Canvas. I still have to transfer them to our actual gradebook.
I can then go back and download the submissions if I want to look at them for style or tips. Generally I try and do this with everybody on at least one lab per lab set.
What I've found is that students average about 11 submissions before they move on to the next lab. I only grade the last one, although I'll go back and look to see how they progressed.
Downside to this is that it works well for smaller labs, but not as much with larger projects. I can break down large projects into pieces that they can check, but eventually there has to be a full project turned in.
Before I moved online I would write a JUnit test for every lab, and usually I'd write two. One that I would include with the starter code and one, more in depth, that I would use to test.
Students could run the test code as many times as they wanted. Then, they'd submit their solutions and I'd run it against the other test code.
Biggest downside is it was pretty time consuming to write unit tests for every lab. I've gotten pretty quick, but it's still a time suck.
Not ideal, but I can pick up a lot about students' code by walking around the room and watching them code.
I do this a lot with projects to get a feel for where the kids are on the project. By the time it's turned in I've already got a pretty good idea on what they've done.
Doesn't scale well though. Biggest class I've ever had was 34 students.
Sometimes I fall into this trap, especially with my second and third year students. I give them labs, they work on their labs, and I assume that they're done correctly if they've been working in class.
Only saving grace on this one is that labs are worth very little and tests make up a majority of their averages. So even with gimmie grades on labs, they can still get hammered on the tests.
Admittedly not a good solution, and one that I'm trying to work my way out of next year.
Skim the code and see if you think it works. Same as the participation, this only really works with smaller assignments and when labs aren't worth all that much.