v8-coverage.js

// V8 6.2 required
'use strict';

const fs = require('fs');
const { Session } = require('inspector');
const { promisify } = require('util');

const session = new Session();
if (session != null) {
  session.connect();
}

const run = promisify(session.post.bind(session));

const NATIVES = process.binding('natives');

function formatCoverage({ url, scriptId, functions }) {
  const isInternal = /^[\w-]+(?:\/[\w-]+)*\.js$/.test(url);
  if (url.includes('internal/fs')) {
    const source = isInternal ?
      NATIVES[url.replace(/\.js$/, '')] : fs.readFileSync(url, 'utf8');

    const markers = [
      {
        startOffset: 0,
        endOffset: source.length,
        count: 0,
      }
    ];
    functions.forEach(f => {
      f.ranges.forEach(range => {
        if (range.count > 0) {
          console.log('covered:\n', source.slice(range.startOffset, range.endOffset));
        }
      });
    });
  }
}

run('Profiler.enable')
  .then(() => run('Profiler.startPreciseCoverage', { detailed: true }))
  .then(() => {
    require('./test/parallel/test-fs-read-file-sync.js');
  })
  .then(() => run('Profiler.takePreciseCoverage'))
  .then((data) => data.result.forEach(formatCoverage))
  .then(() => run('Profiler.stopPreciseCoverage'));