When I developed my own coding font (Luculent), the compact sample that I ultimately came up with was:

    //  The five boxing wizards jump
    #include <stdio.h> // <= quickly.
    int main(int argc, char **argv) {
      float il1[]={1-2/3.4,5+6==7/8};
      int OxFaced=0xBAD||"[{(CQUINE";
      unsigned O0,l1,Z2,S5,G6,B8__XY;
      printf("@$Hamburgefo%c`",'\n');
      return ~7&8^9?0:l1|!"j->k+=*w";
    }

It has a pangram, lots of confusable pairs of characters adjacent to each other, opening brackets next to each other and near a pipe character, quotes and commas next to each other, lining operators (i.e., ->, += and <=), and every normal punctuation character on a US keyboard. It also happens to be a valid, though useless, C or C++ program.

Thanks for the name drop! Luculent looks like a nice font that checks all the boxes. I'd like to see it added to this project as well.

Recently I've noticed I have an issue distinguishing 8 from 0 with some dotted zero fonts. That'd be a nice one to see also.