The setup for the application done by CRAN included Jest, as we saw, and Jest provides us with the coverage option we need. To start, we'll have to add a simple script, to run our suite of tests with a couple of extra parameters:

"scripts": {
    .
    .
    .
    "test": "jest",
    "coverage": "jest --coverage --no-cache",
},

That's all, we don't have anything else to do; let's just see it work!