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Testing FactoryBot Attributes Generation in factory_bot

This test suite validates the attributes_for functionality in FactoryBot, focusing on generating attribute hashes for model instances without persisting them to the database. It covers overriding default values, handling associations, and working with models that have custom constructors.

Test Coverage Overview

The test suite comprehensively covers the attributes_for feature of FactoryBot, examining multiple scenarios:

Default attribute value assignment
Value overriding capabilities
Lazy attribute evaluation
Association handling
Block syntax usage
Custom constructor parameter handling

Implementation Analysis

The testing approach uses RSpec’s describe/it blocks to organize test cases logically. It employs FactoryBot’s syntax methods and model definitions to create a realistic testing environment. The implementation demonstrates both simple and complex factory definitions, including associations and dynamic attribute values.

Technical Details

Testing tools and configuration include:

RSpec as the testing framework
FactoryBot for test data generation
Custom model definitions using define_model helper
Mock database associations (belongs_to, has_many)
Dynamic attribute evaluation

Best Practices Demonstrated

The test suite exemplifies several testing best practices:

Isolated test scenarios with clear setup
Comprehensive edge case coverage
Proper use of before blocks for setup
Clear expectation definitions
Effective use of subject blocks
Proper separation of concerns in test organization

thoughtbot/factory_bot

spec/acceptance/attributes_for_spec.rb

            
if RUBY_ENGINE != "truffleruby"
  require_relative "attributes_for_destructuring"
end

describe "a generated attributes hash" do
  include FactoryBot::Syntax::Methods

  before do
    define_model("User")
    define_model("Comment")

    define_model("Post", title: :string,
      body: :string,
      summary: :string,
      user_id: :integer) do
      belongs_to :user
      has_many :comments
    end

    FactoryBot.define do
      factory :user
      factory :comment

      factory :post do
        title { "default title" }
        body { "default body" }
        summary { title }
        user
        comments do |c|
          [c.association(:comment)]
        end
      end
    end
  end

  subject { attributes_for(:post, title: "overridden title") }

  it "assigns an overridden value" do
    expect(subject[:title]).to eq "overridden title"
  end

  it "assigns a default value" do
    expect(subject[:body]).to eq "default body"
  end

  it "assigns a lazy, dependent attribute" do
    expect(subject[:summary]).to eq "overridden title"
  end

  it "doesn't assign associations" do
    expect(subject).not_to have_key(:user_id)
    expect(subject).not_to have_key(:user)
  end
end

describe "calling `attributes_for` with a block" do
  include FactoryBot::Syntax::Methods

  before do
    define_model("Company", name: :string)

    FactoryBot.define do
      factory :company
    end
  end

  it "passes the hash of attributes" do
    attributes_for(:company, name: "thoughtbot") do |attributes|
      expect(attributes[:name]).to eq("thoughtbot")
    end
  end

  it "returns the hash of attributes" do
    expected = nil

    result = attributes_for(:company) { |attributes|
      expected = attributes
      "hello!"
    }
    expect(result).to eq expected
  end
end

describe "`attributes_for` for a class whose constructor has required params" do
  before do
    define_model("User", name: :string) do
      def initialize(arg1, arg2)
        # Constructor requesting params to be used for testing
      end
    end

    FactoryBot.define do
      factory :user do
        name { "John Doe" }
      end
    end
  end

  subject { FactoryBot.attributes_for(:user) }
  its([:name]) { should eq "John Doe" }
end