ESM in Mocha

_disable_stealthy_require.js

// Disable stealthy-require as it breaks ESM in modernish node

// 1. Load stealthy-require into the require cache. This way all the module
//    machinery gets run like normal.
require("stealthy-require")

// 1. Overwrite the real function with a dummy one
require.cache[require.resolve("stealthy-require")].exports = notSoSthealthyRequire

// 3. Dummy implementation that calls the provided callbacks in the right order
//    but doesn't do anything fancy to the require cache.
function notSoSthealthyRequire(_requireCache, callback, callbackForModulesToKeep, _module) {
  callbackForModulesToKeep()
  return callback()
}

_mocha.mjs

import "./_disable_stealthy_require.js"

import path from "path"
import Mocha from "mocha/lib/mocha"

const { run: originalRun } = Mocha.prototype
Mocha.prototype.run = async function ESM$run(_fn) {
  let { suite } = this

  for (let [index, file] of this.files.entries()) {
    file = path.resolve(file)
    suite.emit("pre-require", global, file, this)
    suite.emit("require", await import(file), file, this)
    suite.emit("post-require", global, file, this)
  }

  return originalRun.apply(this, arguments)
}

Mocha.prototype.loadFiles = function ESM$loadFiles(fn) {
  // The real work has already been done in `run` above
  fn && fn()
}

import cli from "mocha/lib/cli/cli"
cli.main()

coverage

#!/bin/sh

set -e

dir=$(CDPATH="" cd -- "$(dirname -- "$0")" && pwd)
mocha="$dir/_mocha.mjs"

export NODE_ENV=test
export PATH="$dir/../node_modules/.bin":$PATH

# Generate both a report to the terminal, with summary, and a HTML for details.
c8 node --experimental-modules "$mocha" "$@"

mocha

#!/bin/sh

set -e

dir=$(CDPATH="" cd -- "$(dirname -- "$0")" && pwd)
mocha="$dir/_mocha.mjs"

export NODE_ENV=test

node --inspect=9230 --experimental-modules "$mocha" "$@"