Rails 5 Test Prescriptions

Setting Up JavaScript Unit Tests

This is going to be a bit involved, I’m afraid. Rails 5.1 uses the Webpacker gem, which allows you to bypass the Rails asset pipeline and use Webpack—an asset-bundling tool that is in common use by JavaScript developers. Webpack allows you to do all the same things the old Rails asset pipeline does: module lookup, compilation, conversion to a single minified file, and the like. But Webpack is more integrated with current JavaScript tools and makes it much easier to integrate with JavaScript code that is distributed using the Node Package Manager (NPM).^[35]

That’s the good news. The less-good news is that Webpack configuration can be really complicated, especially if you’re a Rails developer and are used to convention ...