exceed_query_limit.rb

RSpec::Matchers.define :exceed_query_limit do |expected|
  supports_block_expectations

  match do |block|
    query_count(&block) > expected
  end

  failure_message_when_negated do |actual|
    "Expected a maximum of #{expected} queries, got #{@recorder.count}:\n\n#{@recorder.log_message}"
  end

  def query_count(&block)
    @recorder = ActiveRecord::QueryRecorder.new(&block)
    @recorder.count
  end
end

query_recorder.rb

module ActiveRecord
  class QueryRecorder
    attr_reader :log
 
    def initialize(&block)
      @log = []
      ActiveSupport::Notifications.subscribed(method(:callback), 'sql.active_record', &block)
    end
 
    def callback(name, start, finish, message_id, values)
      return if %w(CACHE SCHEMA).include?(values[:name])
      @log << values[:sql]
    end

    def count
      @log.count
    end

    def log_message
      @log.join("\n\n")
    end
  end
end

query_recorder_usage.txt

def non_rspec_test
  query_record = ActiveRecord::QueryRecorder.new{ model.some_method }
  assert(query_record.count < 3, query_record.log_message)
end

it "doesn't need excessive database calls" do
  expect{ booking.status_hash }.not_to exceed_query_limit(3)
end

# Alternative usage with control count
it 'avoids excessive database calls' do
  control_count = ActiveRecord::QueryRecorder.new{ booking.status_hash }.count
  create_list(:booking, 10)
  expect{ booking.status_hash }.not_to exceed_query_limit(control_count)
end