The Rules of Code

1. A single file should contain fewer than 20000 lines of code.
2. Make your comments invisible by prefixing "todo". They will never be seen again.
3. It would be nice if a single routine could fit into 1000 lines of code.
4. Use consistent formatting. Even better: don't bother and let clang-format do it.
5. Unit testing is awesome and will almost certainly catch on, see a set of unit testing rules
6. Make everything constant: you should be declaring things as constant as a matter of course and then relaxing it as necessary. It’s much easier to reason about code when the data are immutable.

int main() {
    const struct mostly_immutable {
        int one = 1;
        int two = 2;
        int thr = 3;
        mutable int i_can_change = 4;
    } a;

    a.i_can_change = 5;
}

https://godbolt.org/z/4rWqxb4oq

Unit testing

A test is not a unit test if:

• It talks to the database
• It communicates across the network
• It touches the file system
• It can't run at the same time as any of your other unit tests
• You have to do special things to your environment (such as editing config files) to run it.

See the complete article.