object_double for Mandril::API

When using the mandril-api the Rails Action Mailer is bypassed, so it is not possible to do something like this

it 'sends an email' do
   expect { subject.send_instructions }
     .to change { ActionMailer::Base.deliveries.count }.by(1)
end

I am trying to use an object_double to test my mailers. What I am trying to test is exactly what parameters are sent to the API (via an options hash).

So far, I have the Mandrill code here

  MANDRILL.messages.send_template( options[:template], [], message) unless Rails.env.staging?

Where MANDRILL is just the connection to the API, as detailed below.

describe 'verify content' do
  it 'uses the correct template' do
    api = object_double(Mandrill::API.new(ENV['MANDRILL_KEY']).messages)
    allow(api).to receive(:send_template)
    PostNotificationMailer.format_options(participant, post)
    expect(api).to have_received(:send_template)
    #expect(options[:template]).to eq('crowdai_standard_template')
  end
end

I'd like to be able to check all the params passed to the Mandrill API here. I can mock the messages method but not the messages.send_template

1) PostNotificationMailer verify content uses the correct template
   Failure/Error: expect(api).to have_received(:send_template)

   (ObjectDouble(#<Mandrill::Messages:0x007f8debd4f348 @master=#<Mandrill::API:0x007f8debd4faf0 @host="https://mandrillapp.com", @path="/api/1.0/", @session=#<Excon::Connection:7f8debd4f758 @data={:chunk_size=>1048576, :ciphers=>"HIGH:!SSLv2:!aNULL:!eNULL:!3DES", :connect_timeout=>60, :debug_request=>false, :debug_response=>false, :headers=>{"User-Agent"=>"excon/0.51.0"}, :idempotent=>false, :instrumentor_name=>"excon", :middlewares=>[Excon::Middleware::Hijack, Excon::Middleware::ResponseParser, Excon::Middleware::Expects, Excon::Middleware::Idempotent, Excon::Middleware::Instrumentor, Excon::Middleware::Mock], :mock=>false, :nonblock=>true, :omit_default_port=>false, :persistent=>false, :read_timeout=>60, :retry_limit=>4, :ssl_verify_peer=>true, :ssl_uri_schemes=>["https"], :stubs=>:global, :tcp_nodelay=>false, :thread_safe_sockets=>true, :uri_parser=>URI, :versions=>"excon/0.51.0 (x86_64-darwin15) ruby/2.3.1", :write_timeout=>60, :host=>"mandrillapp.com", :hostname=>"mandrillapp.com", :path=>"", :port=>443, :query=>nil, :scheme=>"https"} @socket_key="https://mandrillapp.com:443">, @debug=false, @apikey="redacted">>) (anonymous)).send_template(*(any args))
       expected: 1 time with any arguments
       received: 0 times with any arguments
 # ./spec/mailers/post_notification_mailer_spec.rb:14:in `block (3 levels) in <top (required)>'

** EDIT **

There is a gem MandrillMailer which solves the problem of testing against the Mandril API, but it's build is broken and it also seems to rebuild the API internally.

How do I test mandrill api with rspec

I couldn't find any tutorials or clear examples on how to use object_double.

Solution

Have you thought about using the VCR gem ( https://github.com/vcr/vcr ) to record the response from the API call to mandrill into a fixture? Once the request is recorded, you can assert the values on the response to verify the expected data was passed.