tailwind.config.js

const IS_DEV = process.env.NODE_ENV === 'development';

let environmentSafelist = [];
if (IS_DEV) {
  environmentSafelist.push({
    pattern: /.+/, // allow everything
  });
}

module.exports = {
  content: [
    "./index.html",
    "./app/**/*.{hbs,js,html}"
  ],
  safelist: [
    'active',
    ...environmentSafelist
  ]
}

I built a self-hosted visual diff testing solution at Groupon. It's work, but doable.

I also wish there was a battle-tested open source solution for this.

There is this https://github.com/garris/BackstopJS