Testing node - filesystem actions

I'm newbie in testing JS so here's my question.

I have function which is using filesystem methods existsSync and mkdirSync. And of course I want to test this function. Should I mock the fs and return simple bool? Should I make the jest to physically create directory and check if it exists?

if (!existsSync(currentPath)) {
            mkdirSync(currentPath);
        }

TL;DR: How to test this code?