Sample posts_controller_spec.rb for https://github.com/rails-api/active_model_serializers/issues/1470

posts_controller_spec.rb

require 'rails_helper'

ActiveModelSerializers.config.schema_path = 'spec/support/schemas'

module ActiveModelSerializers
  module Test
    module Schema
      class AssertSchema
        def controller_path
          request.filtered_parameters.with_indifferent_access[:controller]
        end

        def action
          request.filtered_parameters.with_indifferent_access[:action]
        end
      end

      RSpec::Matchers.define :have_valid_schema do |schema_path|
        match do
          @matcher = AssertResponseSchema.new(schema_path || nil, request, response, nil)
          @matcher.call
        end
        failure_message do
          @matcher.message
        end
      end
    end
  end
end

module ActiveModelSerializers
  module Test
    module Serializer
      extend ActiveSupport::Concern

      def serializer_matches?(expectation)
        @assert_serializer.expectation = expectation
        @assert_serializer.message = message
        @assert_serializer.response = response
        @assert_serializer.matches?
      end

      def message
        @assert_serializer.message
      end

      class AssertSerializer
        def subscribe
          @_subscribers << ActiveSupport::Notifications.subscribe(event_name) do |_name, _start, _finish, _id, payload|
            serializer = payload[:serializer].name
            serializers << serializer
            return unless serializer == 'ActiveModel::Serializer::CollectionSerializer'
            serializers << payload[:adapter].serializer.send(:options)[:serializer].name
          end
        end
      end

      RSpec::Matchers.define :use_serializer do |expected|
        match do
          serializer_matches?(expected)
        end
        failure_message do
          message
        end
      end
    end
  end
end

describe V1::PostsController do
  include ActiveModelSerializers::Test::Serializer
  include ActiveModelSerializers::Test::Schema

  describe '#index' do
    before { get :index }

    describe 'response' do
      subject { response }
      it { is_expected.to use_serializer V1::PostSerializer }
      it { is_expected.to have_valid_schema }
    end
  end
end