Query count RSpec

credits.txt

https://blog.arkency.com/two-ways-for-testing-preloading-eager-loading-of-activerecord-association-in-rails/
https://github.com/monterail/rspec-query-limit

query_count_matcher.rb

# Create a new file: api/spec/support/query_count_matcher.rb
# frozen_string_literal: true

RSpec::Matchers.define :query_limit_eq do |expected|
  match do |block|
    query_count(&block) == expected
  end

  if respond_to?(:failure_message)
    failure_message do |_actual|
      failure_text
    end

    failure_message_when_negated do |_actual|
      failure_text_negated
    end
  else
    failure_message_for_should do |_actual|
      failure_text
    end

    failure_message_for_should_not do |_actual|
      failure_text_negated
    end
  end

  def query_count(&block)
    @counter = 0

    counter = ->(_name, _started, _finished, _unique_id, payload) {
      unless %w[CACHE SCHEMA].include?(payload[:name])
        @counter += 1
      end
    }

    ActiveSupport::Notifications.subscribed(
      counter,
      "sql.active_record",
      &block
    )

    @counter
  end

  def supports_block_expectations?
    true
  end

  def failure_text
    "Expected to run exactly #{expected} queries, got #{@counter}"
  end

  def failure_text_negated
    "Expected to run other than #{expected} queries, got #{@counter}"
  end
end

taxons_controller_spec.rb

# Adding this specs into api/spec/requests/spree/api/taxons_controller_spec.rb:87

context 'filtering by taxon ids' do
  let!(:v2_4) { create(:taxon, name: "2.4", parent: taxon, taxonomy: taxonomy) }
  let!(:v2_4_1) { create(:taxon, name: "2.4.1", parent: v2_4, taxonomy: taxonomy) }

  it 'returns only requested ids' do
    get spree.api_taxons_path, params: { ids: [v2_4_1.id] }

    expect(json_response['taxons'].size).to eq 1
  end

  it 'avoids N+1 queries retrieving several taxons' do
    expect {
      get spree.api_taxons_path, params: { ids: [v2_4.id, v2_4_1.id] }
    }.to query_limit_eq(7)
  end
end