render-runner.js

const path = require('path');

const karma = require('karma');
const Server = karma.Server;

const server = new Server({
  configFile: path.join(__dirname, 'render-karma.conf.js')
}, process.exit.bind(process));

// Make sure dirPath exists and is clean.
// Left as an exercise for the reader.
//
function cleanDir(dirPath, callback) {}

cleanDir(path.join('/', 'visual-diff', 'results'), function(err) {
  if (err) {
    console.error(err);
    return;
  }

  server.start();
});