A lot of the times I see people taking the advice of “make your test cases be in increasing difficulty”, but then they fill the first test case with something that doesn’t represent the problem very well, making you have to look at or run the first test case, which is especially frustrating in CoC.
I’d say there are two good ways to make this a bit simpler. An easy way would be just labeling the first test case as “example test case” or similar, or even example/test case 1. A solution that would help keep the increasing difficulty guideline in order would be adding a radio button set, where you can select which problem should be the example.
Of course what would also be nice is a simple preview of your contribution on the side to make simple mistakes like [[x] easier to spot.