Node.js boilerplate - ES Modules + Mocha + Nyc

Because ESM not really there yet.

Result of a quick research on how to get ESM code to test in Node.js with accurate code coverage reports.

Uses:

• esm
• mocha
• chai
• nyc

Includes:

• Eslint + Prettier config
• VSCode launcher

Getting started

npm ci

npm run test
npm run coverage

Known issues

Breakpoints not always detected

Placing a breakpoint in VSCode does not work all the time. There seems to be an off by one problem, displacing the breakpoint when you execute the tests.

Workaround: debugger works 100%. You will have to temporarily disable eslint/prettier auto fix, as the debugger; statement is automatically removed on save.

Files not exercised by tests are not included in coverage report

Attempting to use all: true in .nycrc causes it to crash with Cannot convert undefined or null to object. Possibly related with this issue: --all is super broken.

Workaround: adding a placeholder test for each file will report the file.

What makes it work

• the --require esm argument, when running _mocha

• the "require": ["esm"] setting, in .nycrc

  "require": [
    "esm"
  ],

• the cjs: true setting, in package.json

  "esm": {
    "cjs": true
  },

Kudos

Kudos:

• all the people trying hard out there
• John-David Dalton's ESM package
• ESM Zero Configuration
• dschnare/std-esm-sandbox - older boilderplate that was still using the deprecated @std/esm
• Native ES Modules in NodeJS: Status And Future Directions - good read
• Testing in ES6 with Mocha and Babel 6 - another good read, even if Babel is no longer required here

MIT License

Copyright (c) 2017 Andre Torgal

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.