README

🎩`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 mock modules without mock-require (we in `ESM`!);

☝️ that's solved! mock-import does the thing using loaders;

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

☝️ c8 could help, but no it supports no query paramters 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

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.

What if I want to use 🎩`ESCover` with `mock-import`?

Experimental loaders supports only one, for now. So zenload should be used.

Install it with:

npm i escover mock-import zenload

Then run:

NODE_OPTIONS="'--loader zenlend'" ZENLOAD='escover,mock-import' escover npm test

What you should know about `lcov`

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

☝️ lcov was created in 2002, almost 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 recored for current file entry;

The only thing that is differ from lcov: counters it 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

Usage no npm install needed!

README

🎩ESCover