Missing note on stubbing ServiceActor::Result

[Josua Schmid]

I'm trying to fake a service actor result in a Rails request spec. The test I would like to write looks like this:

context 'when search fails (e.g. because of HTTP 503 on Google side)' do
  let(:params) { { query: 'Darkstorm Galaxy' } }

  before do
    allow(Google::AutocompletePlaces).to receive(:result).and_return(
      instance_double(ServiceActor::Result, success?: false, error: 'lol')
    )
  end

  it 'returns suggestions' do
    get api_authenticated_address_search_suggestions_path, params: params, headers: auth_headers

    expect(response).to have_http_status(:service_unavailable)
    expect(response.parsed_body).to include('application_errors' => be_a(String))
  end
end

But this doesn't work because error is derived from method_missing. And I shouldn't use double because of RSpec best practices enforced by rubocop.

What's your take on that?

[Sunny Ripert]

RSpec couldn’t be able to know what methods are defined on results since these methods only make sense at the end, once it’s passed through different actors.

For your example, it would make sense to define an error method on ServiceActor::Result for this specific use case, as it’s an encouraged output name:

class ServiceActor::Result
  def error
    to_h[:error]
  end
end

However, this still wouldn’t work for other defined outputs.

You could use an instance_double and stub expected outputs with allow:

let(:result) { instance_double ServiceActor::Result, success?: false }

before do
  allow(Google::AutocompletePlaces).to receive(:result).and_return(result)
  allow(result).to receive(:error).and_return("lol")
end

In my case, though, I simply use double in these cases and disable this cop, since it can’t know when we can and cannot check the methods beforehand:

RSpec/VerifiedDoubles:
  # Allow the use of `double`.
  Enabled: false

[Paulo Fidalgo]

For those landing here but living on the minitest land: https://fidalgo.pt/2023/07/23/service-objects-in-the-wild.html
(shameless plug)

[Sunny Ripert]

Great thorough article! I’ve added it to the list of resources on the wiki

[Sunny Ripert]

I’m closing this issue, but feel free to discuss/reopen if you think of a better way to handle this.