How to get coverage up and working

[gomain]

In Jest, coverage reporting is just a matter of switching it on. The coverage report section in the README presumes great knowledge about how things work under the hood. I.e. what's babel, what's istanbul, what's a loader, what are these plugins, what's this config for...

Could anyone help point out how to setup a project such that we get coverage reporting with plain Jest and this runner, nothing else.

A how to for dummies, if you may.
Thankyou.

[gomain]

So I'v finally got it working.

1. Install "babel-register-esm", save dev
2. In ./jest.config.mjs

   collectCoverage: true,
   coverageProvider: "babel",
   coverageReporters: ["text"],

3. Add file ./babel.config.json

   {
     "plugins": ["babel-plugin-istanbul"]
   }

4. Run tests with NODE_OPTIONS='--loader=babel-register-esm' jest
   

[gomain]

I have some confusions.

1. The ./babel.config.json specifies a plugin which I didn't install.
2. The "babel-register-esm" loader has a peer dependency "@babel/core" which I didn't install.

Yet coverage report works. Why?