The goal is to get Jasmine specs running in a Rails project using Webpacker, with the browser based test runner. Should be easily adaptable to a pure Webpack setup.

Step 1: Install Jasmine

Copy
yarn add jasmine-core

Step 2: Add two separate packs

Since we do not want to mix Jasmine into our regular Javascript, we will create two additional packs. The first only contains Jasmine and the test runner. The second will contain our normal application code and the specs themselves.

We cannot combine both into a single pack, since this will confuse Jasmine and cause it to swallow all backtraces.

Copy
// app/webpack/packs/jasmine.js

import 'jasmine-core/lib/jasmine-core/jasmine.css'

import 'jasmine-core/lib/jasmine-core/jasmine-html.js'
import 'jasmine-core/lib/jasmine-core/boot.js'

import 'jasmine-core/images/jasmine_favicon.png'

Copy
// app/webpack/packs/specs.js
// First load your regular JavaScript (copy all the JavaScript imports from your main pack).
// For example:

import 'unpoly/dist/unpoly.js'
let webpackContext = require.context('../javascripts', true, /\.js(\.erb)?$/)
for(let key of webpackContext.keys()) { webpackContext(key) }


// Then load the specs

let specsContext = require.context('../spec', true, /\.js(\.erb)?$/)
for(let key of specsContext.keys()) { specsContext(key) }

You packs might not live in app/webpack, so adjust depending on your setup.

Lastly, add a sample spec to app/webpack/spec/, like

Copy
// app/webpack/spec/test_spec.js
describe('The truth', () => {
  it('is still true', () => {
    expect(true).toBe(true)
  })
})

Step 3: Add the Webpack ProvidePlugin for Jasmine

In your config/webpack/environment.js, add

Copy
const webpack = require('webpack')

environment.plugins.prepend('Provide', new webpack.ProvidePlugin({
  jasmineRequire: 'jasmine-core/lib/jasmine-core/jasmine.js',
}))

Step 4: Add a /jasmine page in Rails

Copy
# config/routes.rb

Rails.application.routes.draw do
  # ...

  if Rails.env.development? || Rails.env.test?
    get 'jasmine', to: 'jasmine#index'
  end
end

Copy
# app/controllers/jasmine_controller.rb

class JasmineController < ApplicationController
  layout false

  def index
  end
end

Copy
-# app/views/jasmine/index.html.haml

!!!
%html
  %head
    = stylesheet_pack_tag 'jasmine', :media => 'all'
    %link{href: image_path('jasmine_favicon.png'), rel: 'icon', type: 'image/png'}

  %body
    = javascript_pack_tag 'jasmine'
    = javascript_pack_tag 'specs'

Step 5: Enjoy

Go to /jasmine and see your (hopefully) working setup.

Bonus step: add jasmine-ajax

To add the jasmine-ajax addon, you need to

Copy
yarn add jasmine-ajax

Then add it to the pack

Copy
// app/webpack/packs/spec.js

// after the other jasmine imports
import 'jasmine-ajax'

You also need a customer provider. Add a file

Copy
// app/webpack/spec/support/jasmine_provider.js
import jasmineRequire from 'jasmine-core/lib/jasmine-core/jasmine.js'

export default function getJasmineRequireObj() {
  return jasmineRequire;
}

Then in your config/environment.js, add another option to the Provide plugin:

Copy
environment.plugins.prepend('Provide', new webpack.ProvidePlugin({
  jasmineRequire: 'jasmine-core/lib/jasmine-core/jasmine.js', // already there
  getJasmineRequireObj: ['spec/support/jasmine_provider.js', 'default'],
}))