ruby on rails - RSpec: Can't seem to stub ActiveRecord::QueryMethods#select -

i'm trying write test computes average of many db records without overhead of reading/writing db.

here method:

class average::route   def self.daily_flight_count     route.active.map |r|       times = r.flights.select('distinct depart_time').count       (times / 7.0).round     end.average   end end 

the method gets number of unique depart times per day routes , averages average route's daily flight count.

i'm setting test so:

require 'rails_helper'  describe average::route   describe '.daily_flight_count'     'returns average daily flight count of routes'       flights1 = (1..7).inject([]) |arr, n|         arr << double(flight, depart_time: time.now + n.days)       end        flights2 = (1..7).inject([]) |arr, n|         arr << double(flight, depart_time: time.now + n.days)         arr << double(flight, depart_time: time.now + n.days)       end        r1 = double(route, flights: flights1)       r2 = double(route, flights: flights2)        allow(route).to receive(:active).and_return([r1, r2])       allow(flights1).to receive(:select).and_return(flights1.map(&:depart_time))       allow(flights2).to receive(:select).and_return(flights2.map(&:depart_time))        expect(average::route.daily_flight_count).to eq(1)     end   end end 

based on how r1 , r2 doubles of route set return arrays of flight doubles, ran problem since array responds #select differently activerecord relation (how behave), tried stub flights1 , flights2 arrays return mapped depart times. however, when run test still error:

failures:    1) average::route.daily_flight_count returns average daily flight count of routes      failure/error: expect(average::route.daily_flight_count).to eq(1)      argumenterror:        wrong number of arguments. expected 0, got 1.      # ./app/models/average/route.rb:14:in `block in daily_flight_count'      # ./app/models/average/route.rb:13:in `map'  

the stubs flights1 , flights2 don't seem working. error still calling activerecord #select method on array of doubles , failing because array#select takes block , code gives argument (since in production collection relation).

any ideas on how working?

you'll need specify parameters you're expecting

 allow(flights1).to receive(:select).with('distinct depart_time').and_return(flights1.map(&:depart_time))