opal-rspec allows opal to use rspec for running specs in javascript environments. It comes with built-in support for running rspec with standard web browser formatters. Also, async spec examples are supported to reflect browser usage of ruby applications.

describe User do
  it "can be created with a name" do
    expect( be_persisted


Add the opal-rspec gem to your Gemfile:

# Gemfile
gem 'opal'
gem 'opal-rspec'

Running specs

In a Browser

opal-rspec can use sprockets to build and serve specs over a simple rack server. Add the following to a file:

require 'bundler'

sprockets_env =
run sprockets_env) { |s|
  s.main = 'opal/rspec/sprockets_runner'
  s.append_path 'spec'
  s.debug = false

Then run the rack server bundle exec rackup and visit http://localhost:9292 in any web browser.

Async examples

opal-rspec adds support for async specs to rspec. These specs are defined using #async instead of #it:

describe MyClass do
  # normal example
  it 'does something' do
    expect(:foo).to eq(:foo)

  # async example
  async 'does something else, too' do
    # ...

This just marks the example as running async. To actually handle the async result, you also need to use a run_async call inside some future handler:

async 'HTTP requests should work' do
  HTTP.get('/users/1.json') do |res|
    run_async {
      expect(res).to be_ok

The block passed to run_async informs the runner that this spec is finished so it can move on. Any failures/expectations run inside this block will be run in the context of the example.