puppeteer-test.js

const fs = require('fs');
const path = require('path');
const { EventEmitter } = require('events');
const express = require('express');
const karma = require('karma');
const ngCLIKarmaPlugin = require('@angular/cli/plugins/karma');
const puppeteer = require('puppeteer');
const mkdirp = require('mkdirp');
const rimraf = require('rimraf');

class Emitter extends EventEmitter {
  refreshFiles() {          // Called by karma plugin
    this.emit('ready');
  }
}

function createServer(port) {
  const app = express();
  const emitter = new Emitter();
  const handlers = [];      // karm plugin will push something like { handler: webpack-dev-middleware }.
  const testConfig = karma.config.parseConfig(path.resolve('./karma.conf.js'));
  const init = ngCLIKarmaPlugin['framework:@angular/cli'][1];
  init(testConfig, emitter, handlers); // conf, emitter, customFileHandlers,
  app.use(express.static(__dirname));
  app.use(handlers[0].handler);
  const server = {
    app,
    shutdown: () => new Promise(resolve => emitter.emit('exit', resolve)),
  };
  return new Promise((resolve, reject) => emitter.once('ready', () => app.listen(port, () => resolve(server))));
}

async function runPuppeteer() {
  const browser = await puppeteer.launch({ args: ['--no-sandbox', '--disable-setuid-sandbox'] });
  const page = await browser.newPage();

  // Capture logging
  page.on('console', (...args) => console.log.apply(console, ['[Browser]', ...args]));

  // Expose Screenshot function
  await page.exposeFunction('capturePage', name => {
    const filename = path.resolve(__dirname, `actual_images/${name}.png`);
    console.log('[Node]', 'Save 🎨  to', filename);
    return page.screenshot({ path: filename, fullPage: true });
  });

  const server = await createServer(3100);

  await page.exposeFunction('puppeteerDone', async code => {
    await server.shutdown();
    process.exit(code);
  });

  await page.goto('http://localhost:3100/test/context.html');
}

rimraf.sync('actual_images/**/*.png');
mkdirp.sync('actual_images');

runPuppeteer();