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Puffing-billy stub creating and request cache

Some feature tests excercise application logic that includes aysnchronous javascript calls to external services (APIs). In particular, searching for proceedings and organisations is achieved this through ajax calls to the legal-framework-api. VCR does not intercept browser calls therefore puffing-billy is used. This provides a "rewriting web proxy" to intercept and stub the calls.

VCR and puffing-billy can be used together to achieve stubbing of any calls to external services from the backend and frontend respectively.

Setup

Legal Framework API

This service is explictly called from javascript to search for proceedings and organisations. Therefore we must ensure .env.test has LEGAL_FRAMEWORK_API_HOST pointing to staging environment.

Stubbing

While it is possible to record and playback requests, using puffing-billy, in a manner similar to vcr, stubbing a request is the preferred option. To add a stub you should add or extend helper methods in the features/support/puffing_billy_helper.rb and then call that in a cucumber step definition that will make the call you wish to stub.

# features/support/puffing_billy_helper.rb
def stub_my_call
  proxy
    .stub("https://legal-framework-api-staging.cloud-platform.service.justice.gov.uk:443/proceeding_types/searches", method: "post")
    .and_return(
      headers: {
        "Access-Control-Allow-Origin" => "*",
      },
      code: 200,
      body: { key: "value", another_key: "another_value" }.to_json,
    )
end

And use

When("I do something that calls a service via ajax") do
  stub_my_call

  fill_in("some-input-that-makes-ajax-call", with: 'whatever')
end

Request caching (recording)

If you want to record a request and response, either to use in a feature test or to use to create a stub (before deleting it), you can:

  1. comment out/remove any proxy.stubs already in use by the feature

  2. amend the puffing-billy config in features/support/puffing_billy.rb

    • set non_whitelisted_requests_disabled = false
    • ensure cache = true and persist_cache = true

  3. run the feature (with debug to view request being made of billy's proxy)

DEBUG_BILLY=true cucumber features/providers/applicant_details.feature:3
  1. The requests should appear in the configured folder features/puffing-billy/request_cache

Warning: you may also need to configure Billy to record certificates temporarily. You SHOULD NOT commit these to the repo.

# features/support/puffing_billy.rb
Billy.configure do |c|
  ...
  c.certs_path = 'features/puffing-billy/request_certs'
  ...
end

To rerecord a request cache simply delete the file and rerun the feature.

Debugging

You can display all calls that puffing-billy proxied using an env var as below.

DEBUG_BILLY=true cucumber features/providers/applicant_details.feature:3