Your Test Suite is Making Too Many Database Calls!

Originally given at RailsConf 2022. Recording at https://www.youtube.com/watch?v=LOlG4kqfwcg

On a recent project, I sped up a test suite 15% by making a change to a single factory. This suite, like many others (including yours!), was making way too many database calls. It’s so easy to accidentally add extra queries to factories and test setup and these can compound to shockingly large numbers.

The chaos is your opportunity! Learn to profile and fix hot spots, build big-picture understanding through diagrams, and write code that is resistant to extraneous queries. This talk will equip you to take back control of your build times and maybe impress your teammates in the process.

Transcript

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8. # BAD
   
   it "#full_name concatenates first and last name" do
   
   user = create(
   
   :user,
   
   first_name: "Joël",
   
   last_name: "Quenneville"
   
   )
   
   expect(user.full_name).to eq "Joël Quenneville"
   
   end
   

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9. # GOOD
   
   it "#full_name concatenates first and last name" do
   
   user = User.new(
   
   first_name: "Joël",
   
   last_name: "Quenneville"
   
   )
   
   expect(user.full_name).to eq "Joël Quenneville"
   
   end
   

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19. let(:user1) { create(:user) }
    
    let(:user2) { create(:user) }
    
    let(:organization) { create(:organization), users: [user1, user2] }
    
    
    
    # this test only needs an org
    
    it "does something"
    
    
    
    # this test needs and org + some users
    
    it "does something whith multiple users"
    

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25. let(:contact) { create(:contact) }
    
    let(:user) { create(:user, admin: true, contacts: [contact]) }
    
    
    
    # NEEDS 1 query
    
    # MAKES 3 queries (2x CREATE + 1x UPDATE)
    
    it "does something for a regular user" do
    
    user.update(admin: false)
    
    ...
    
    end
    
    
    
    # NEEDS 2 queries
    
    # MAKES 2 queries
    
    it "does something for an admin with contact info"
    

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27. # this test only needs an org
    
    it "does something" do
    
    org = create(:organization)
    
    
    
    ...
    
    end
    
    
    
    # this test needs and org + some users
    
    it "does something whith multiple users" do
    
    user1 = create(:user)
    
    user2 = create(:user)
    
    org = create(:organization, users: [user1, user2]
    
    
    
    ...
    
    end
    

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34. factory :organization do
    
    members { create_list(:user, 3 }
    
    sequence(:name) { |n| "Organization #{n}" }
    end
    

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35. it "does something" do
    
    # this makes 4 INSERT queries
    
    org = create(:organization)
    
    expect(org.do_something).to eq "something"
    
    end
    

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37. factory :organization do
    
    members { create_list(:user, 3 }
    
    sequence(:name) { |n| "Organization #{n}" }
    end
    
    
    
    factory :user do
    
    association :organization
    
    end
    

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38. it "does something given a user" do
    
    user = create(:user)
    
    service = MyService.new(user)
    
    
    
    expect(service.call()).to eq "something"
    
    end
    

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41. factory :organization do
    
    sequence(:name) { |n| "Organization #{n}" }
    end
    

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42. factory :organization do
    
    sequence(:name) { |n| "Organization #{n}" }
    
    
    
    trait :with_users do
    
    members { create_list(:user, 3 }
    
    end
    end
    

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44. ActiveSupport::Notifications.
    
    subscribe("factory_bot.run_factory")
    

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45. [TEST PROF INFO] Factories usage
    
    
    
    Total: 15285
    
    Total top-level: 10286
    
    Total time: 04:31.222 (out of 07.16.124)
    
    Total uniq factories: 119
    
    
    
    total top-level total time time per call top-level time name
    
    6091 2715 115.7671s 0.0426s 50.2517s user
    
    2142 2098 93.3152s 0.0444s 92.1915s post
    
    ...
    

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48. class Organization < ApplicationRecord
    
    before_create :generate_admin
    
    
    
    def generate_admin
    
    admin = User.create!(
    
    email: "admin@#{organization.domain}",
    
    admin: true
    
    )
    
    self.admin = admin
    
    end
    
    end
    

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49. it "does something" do
    
    admin = create(:user, admin: true)
    
    org = create(:organization, admin: admin)
    
    
    
    # ...
    
    end
    

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52. it "does something" do
    
    admin = create(:user, admin: true)
    
    org = create(:organization)
    
    
    
    # CODE SMELL!
    
    # This now makes 3 INSERTs + 1 UPDATE calls
    
    org.update(admin: admin)
    
    
    
    # ...
    
    end
    

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56. factory_bot_results = {}
    
    config.before(:suite) do
    
    ActiveSupport::Notifications.subscribe("factory_bot.run_factory") do |name, start,
    finish, id, payload|
    
    # aggregate results
    
    end
    
    
    
    config.after(:suite) do
    
    puts factory_bot_results
    
    end
    

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61. factory :organization_with_events do
    
    staff { create_list(:staff, 1) }
    
    venues { create_list(:venue, 1)
    
    
    
    after(:build) do |org|
    
    create_list(:event, 3, venue: org.venues.first)
    
    end
    
    end
    

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62. factory :organization_with_events do
    
    staff { create_list(:staff, 1) }
    
    venues { create_list(:venue, 1)
    
    
    
    after(:build) do |org|
    
    create_list(:event, 3, venue: org.venues.first, staff: org.staff.first)
    
    end
    
    end
    

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