Daily Bulletin


The Conversation

  • Written by James Healy, Technical Director, The Conversation

Rails encourages developers to use a database in integrated acceptance tests, and we’ve gone with the flow on that front.

However, like many rails apps we also integrate with a number of external services that are more difficult to deal with in tests - stripe, campaign monitor, akismet and slack are good examples. In most cases these services are accessed over the internet and operated by external companies, so to keep our tests fast and reliable we’ve opted to stub them rather than change any remote state.

To begin with, we were inconsistent with where and how we stubbed these services, exploring solutions like rspec mocks, vcr and plain webmock.

As our product grew and we integrated new services, we started to look for a pattern we could standardise on. Our goals for the new pattern were:

  • Avoid all network activity to external services during tests
  • Encourage happy path acceptance tests to avoid excessive build times
  • Rely on unit tests to thoroughly test code that calls the external service, including error cases and intermittent network issues
  • Avoid excessive setup for acceptance tests
  • If we’re using an external gem, encapsulate it with code we own to simplify future refactoring

We settled on a pattern we called “Gateway Objects”, inspired by a Martin Fowler refactoring article.

We store them in app/gateways/ and have added the following line to config/application.rb so rails can find them:

config.autoload_paths << Rails.root.join("gateways").to_s

In most cases we use a fraction of the external service’s functionality, so our gateway classes have public methods for just the bits we need. Each method has extensive unit specs, usually relying on webmock to avoid hitting a live HTTP API.

Where possible, our gateways return objects that are either from ruby core (Integers, Strings, Hashes, Arrays, etc) or immutable value objects that we control.

Here’s a simplified example that adds subscribers to a Campaign Monitor list. It relies on the createsend gem, and uses webmock for unit specs.

require 'createsend'

class CampaignMonitorListGateway
  def initialize(list_id, api_key: nil)
    @list_id = list_id
    @api_key = api_key || ENV.fetch("CAMPAIGN_MONITOR_KEY")
  end

  # add a new email address to this list
  #
  def subscribe(email)
    CreateSend::Subscriber.add(
      {api_key: @api_key},
      @list_id,
      email,   # email address
      email,   # name
      [],      # custom fields
      false    # resubscribe
    ) == email
  end
end

Exhaustive unit specs allow us to focus our integrated acceptance tests on a happy path, so we usually stub the gateway to return a consistent result across all tests with the some configuration in spec/rails_helper.rb:

RSpec.configure do |config|
  config.before :each, type: :feature, stub_cm_list: true do
    allow(CampaignMonitorListGateway).to receive(:new) {
      instance_double(CampaignMonitorListGateway, subscribe: true)
    }
  end
end

With that, any acceptance test can use metadata to declare a need for stubbing.

feature 'A reader subscribing to our daily newsletter' do
  scenario "from a topbar link", :js, :stub_cm_list do
    # some assertions
  end
end

Most method calls on a gateway class will result in network activity and lots can go wrong when networks are involved. We avoid silently swallowing exceptions, and either:

  • catch the exception, notify our error tracker, and return a Null object; or
  • allow the exception to bubble out so the caller deals with it

We’re pretty happy with the final result – our test setup is cleaner, the tests are acceptably fast and pass without internet access, and the shared vocabulary helps us maintain team code in a consistent style over time.

Authors: James Healy, Technical Director, The Conversation

Read more http://theconversation.com/gateway-classes-a-pattern-for-interacting-with-external-services-65633

Writers Wanted

No Barnaby, 2050 isn't far away. Next week's intergenerational report deals with 2061

arrow_forward

Tips For Good SEO In The Law Sector

arrow_forward

The Conversation
INTERWEBS DIGITAL AGENCY

Politics

Prime Minister interview with Karl Stefanovic and Allison Langdon

Karl Stefanovic: PM, good morning to you. Do you have blood on your hands?   PRIME MINISTER: No, it's obviously absurd. What we're doing here is we've got a temporary pause in place because we'v...

Karl Stefanovic and Allison Langdon - avatar Karl Stefanovic and Allison Langdon

Prime Minister Scott Morrison delivered Keynote Address at AFR Business Summit

Well, thank you all for the opportunity to come and be with you here today. Can I also acknowledge the Gadigal people, the Eora Nation, the elders past and present and future. Can I also acknowled...

Scott Morrison - avatar Scott Morrison

Morrison Government commits record $9B to social security safety net

The Morrison Government is enhancing our social security safety net by increasing support for unemployed Australians while strengthening their obligations to search for work.   From March the ...

Scott Morrison - avatar Scott Morrison

Business News

Victorian businesses can claim a rebate on COVID-19 deep cleans until 30 June - but many remain unaware

With exposure sites on the rise and financial stresses already on most Victorian businesses, the recent Business Victoria announcement of a substantial 80% COVIDSafe Deep cleaning rebate is a time...

Article by Damien Smith, CEO of Prime Group - avatar Article by Damien Smith, CEO of Prime Group

Six Tips to Get your Business Known on Social Media

Social media is one of the most effective ways to market your brand to the masses. With the meteoric rise in popularity of various social media platforms over the past decade, millions of brands h...

NewsServices.com - avatar NewsServices.com

Boom in Aussies buying up restaurants, pubs, hotels and bars in regional centres

With international borders closed, regional Australia is seeing a dramatic surge in popularity as people move out of the cities and into their quaint communities. City slickers are looking for new...

Tess Sanders Lazarus - avatar Tess Sanders Lazarus