🎩ESCover

Coverage for EcmaScript Modules based on 🐊Putout and loaders.

Why another coverage tool?

When you want to use ESM in Node.js without transpiling to CommonJS (that's what jest, ava, tap does), you have a couple problems to solve.

🤷‍ What test runner does no transpiling to CommonJS?

☝️ that's easy! 📼 Supertape supports ESM from the box;

🤷‍ How to get coverage when nyc doesn't supported?

☝️ c8 could help, but no it supports no query parameters which are needed to load module again, and apply mocks.

🤷‍ How to get coverage when mocks are used?

☝️ Use 🎩ESCover! It supports loaders, ESM and collects coverage as a loader!

🤷‍ What with coveralls? Does lcov supported?

☝️ Sure! coverage/lcov.info is main coverage file for 🎩ESCover.

Install

npm i escover -D

Run to collect and show coverage:

escover npm test

Comparison with c8

Check out the real example from wisdom. There is next uncovered code:

import {jessy} from 'jessy';

export default (info) => typeof jessy('publishConfig.access', info) === 'undefined';

c8 shows three columns with 100% and one with 0%.

And here is what you will see with 🎩ESCover:

So if you need more accurate code with no bullshit green 100%, use 🎩ESCover 😉.

Config

exclude section of configuration file .nyrc.json supported.

How it looks like?

When everything is covered:

What formatters exists?

There is two types of formatters:

• lines adds links to each line;
• files shows information in table;

You can choose formatter with ESCOVER_FORMAT env variable.

Env

If you want to disable coverage on status code without erroring, use ESCOVER_SUCCESS_EXIT_CODE:

import {SKIPPED} from 'supertape/exit-codes';

const env = {
    ESCOVER_SUCCESS_EXIT_CODE: SKIPPED,
};

export default {
    test: () => [env, `escover tape 'test/**/*.js' 'lib/**/*.spec.js'`],
};

What should I know about lcov?

Format used by 🎩ESCover located in coverage/lcov.info.

• ☝️ lcov was created in 2002, twenty years ago.
• ☝️ Linux kernel developers created it to know what is going on with the coverage.
• ☝️ It's written in PERL and has text based format.
• ☝️ This is most popular coverage format of all times supported by a lot of tools (like coveralls).

When you run your ESM application with:

escover npm test

You will receive something similar to:

SF:/Users/coderaiser/escover/lib/transform.js
DA:1,1
DA:3,1
DA:7,1
DA:9,1
DA:10,1
DA:12,1
DA:24,1
DA:25,1
DA:27,1
DA:28,1
DA:29,1
DA:32,1
end_of_record

Where:

• SF - is path to source;
• DA - is line number, and count of running;
• end_of_record latest recorded for current file entry;

The only thing that is differ from lcov: counters are 0 or 1, if you have a reason to use "real" counters create an issue.

It can be added in one line of code, but I see no reason why it can be useful 🤷‍♂️.

License

MIT