Add Railtie, RSpec/Minitest auto-generation, install generator, and README rewrite

- Add FixtureBot::Rails.generate with auto-detection of fixtures file and output dir
- Add Railtie with config.fixturebot namespace and fixturebot:generate rake task
- Add require "fixturebot/rspec" (before :suite hook) and "fixturebot/minitest" (require-time)
- Add rails generate fixturebot:install for scaffolding
- Add spec for FixtureBot::Rails.generate
- Add spec for explicit nil shadowing generators
- Rewrite README with fixtures-vs-factories motivation, Rails setup docs, and clearer generator examples

Author: bradgessler

README.md

@@ -0,0 +1,5 @@
+# frozen_string_literal: true
+
+require "fixturebot/rails"
+
+FixtureBot::Rails.generate

lib/fixturebot/minitest.rb

@@ -3,3 +3,53 @@
 require "fixturebot"
 require_relative "rails/schema_loader"
 require_relative "rails/cli"
+require_relative "rails/railtie" if defined?(::Rails::Railtie)
+
+module FixtureBot
+  module Rails
+    def self.generate(fixtures_file: nil, output_dir: nil)
+      fixtures_file = resolve_fixtures_file(fixtures_file)
+      return unless fixtures_file && File.exist?(fixtures_file)
+
+      output_dir = resolve_output_dir(output_dir, fixtures_file)
+
+      schema = SchemaLoader.load
+      fixture_set = FixtureBot.define_from_file(schema, fixtures_file)
+      YamlDumper.new(fixture_set).dump(output_dir)
+    end
+
+    def self.resolve_fixtures_file(explicit)
+      return explicit if explicit
+
+      if defined?(::Rails::Railtie) && ::Rails.application&.config&.respond_to?(:fixturebot)
+        configured = ::Rails.application.config.fixturebot.fixtures_file
+        return configured if configured
+      end
+
+      detect_fixtures_file
+    end
+    private_class_method :resolve_fixtures_file
+
+    def self.resolve_output_dir(explicit, fixtures_file)
+      return explicit if explicit
+
+      if defined?(::Rails::Railtie) && ::Rails.application&.config&.respond_to?(:fixturebot)
+        configured = ::Rails.application.config.fixturebot.output_dir
+        return configured if configured
+      end
+
+      detect_output_dir(fixtures_file)
+    end
+    private_class_method :resolve_output_dir
+
+    def self.detect_fixtures_file
+      %w[test/fixtures.rb spec/fixtures.rb].find { |f| File.exist?(f) }
+    end
+    private_class_method :detect_fixtures_file
+
+    def self.detect_output_dir(fixtures_file)
+      fixtures_file.sub(/\.rb\z/, "")
+    end
+    private_class_method :detect_output_dir
+  end
+end

lib/fixturebot/rails.rb

@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+module FixtureBot
+  module Rails
+    class Railtie < ::Rails::Railtie
+      config.fixturebot = ActiveSupport::OrderedOptions.new
+
+      rake_tasks do
+        namespace :fixturebot do
+          desc "Generate YAML fixture files from FixtureBot DSL"
+          task generate: :environment do
+            FixtureBot::Rails.generate
+          end
+        end
+      end
+    end
+  end
+end

lib/fixturebot/rails/railtie.rb

@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+require "fixturebot/rails"
+
+RSpec.configure do |config|
+  config.before(:suite) do
+    FixtureBot::Rails.generate
+  end
+end

lib/fixturebot/rspec.rb

@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+require "rails/generators"
+
+module Fixturebot
+  class InstallGenerator < ::Rails::Generators::Base
+    source_root File.expand_path("templates", __dir__)
+
+    desc "Set up FixtureBot in your Rails application"
+
+    def create_fixtures_file
+      if rspec?
+        template "fixtures.rb.tt", "spec/fixtures.rb"
+      else
+        template "fixtures.rb.tt", "test/fixtures.rb"
+      end
+    end
+
+    def inject_require_into_helper
+      if rspec?
+        inject_into_file "spec/rails_helper.rb",
+          "require \"fixturebot/rspec\"\n",
+          after: "require 'rspec/rails'\n"
+      else
+        inject_into_file "test/test_helper.rb",
+          "require \"fixturebot/minitest\"\n",
+          after: "require \"rails/test_help\"\n"
+      end
+    end
+
+    private
+
+    def rspec?
+      File.directory?(File.join(destination_root, "spec"))
+    end
+  end
+end

lib/generators/fixturebot/install_generator.rb

@@ -0,0 +1,12 @@
+FixtureBot.define do
+  # Define your fixtures here. Example:
+  #
+  #   user :alice do
+  #     name "Alice"
+  #     email "alice@example.com"
+  #   end
+  #
+  #   user :bob do
+  #     name "Bob"
+  #   end
+end

lib/generators/fixturebot/templates/fixtures.rb.tt

@@ -0,0 +1,104 @@
+# frozen_string_literal: true
+
+require "fixturebot/rails"
+require "tmpdir"
+
+RSpec.describe FixtureBot::Rails, ".generate" do
+  before do
+    ActiveRecord::Base.establish_connection(adapter: "sqlite3", database: ":memory:")
+
+    ActiveRecord::Schema.define(version: 2024_01_01_000000) do
+      create_table "users", force: :cascade do |t|
+        t.string "name"
+        t.string "email"
+        t.timestamps
+      end
+
+      create_table "posts", force: :cascade do |t|
+        t.string "title"
+        t.text "body"
+        t.integer "author_id"
+        t.timestamps
+      end
+
+      add_foreign_key "posts", "users", column: "author_id"
+    end
+  end
+
+  after do
+    ActiveRecord::Base.connection_pool.disconnect!
+  end
+
+  it "generates YAML fixture files from a DSL file" do
+    Dir.mktmpdir do |tmpdir|
+      fixtures_file = File.join(tmpdir, "fixtures.rb")
+      output_dir = File.join(tmpdir, "fixtures")
+
+      File.write(fixtures_file, <<~RUBY)
+        FixtureBot.define do
+          user :alice do
+            name "Alice"
+            email "alice@example.com"
+          end
+
+          user :bob do
+            name "Bob"
+            email "bob@example.com"
+          end
+
+          post :hello do
+            title "Hello World"
+            body "First post"
+            author :alice
+          end
+        end
+      RUBY
+
+      described_class.generate(fixtures_file: fixtures_file, output_dir: output_dir)
+
+      users_yaml = YAML.load_file(File.join(output_dir, "users.yml"))
+      expect(users_yaml.keys).to contain_exactly("alice", "bob")
+      expect(users_yaml["alice"]["name"]).to eq("Alice")
+      expect(users_yaml["alice"]["email"]).to eq("alice@example.com")
+      expect(users_yaml["bob"]["name"]).to eq("Bob")
+
+      posts_yaml = YAML.load_file(File.join(output_dir, "posts.yml"))
+      expect(posts_yaml.keys).to contain_exactly("hello")
+      expect(posts_yaml["hello"]["title"]).to eq("Hello World")
+    end
+  end
+
+  it "skips empty tables" do
+    Dir.mktmpdir do |tmpdir|
+      fixtures_file = File.join(tmpdir, "fixtures.rb")
+      output_dir = File.join(tmpdir, "fixtures")
+
+      File.write(fixtures_file, <<~RUBY)
+        FixtureBot.define do
+          user :alice do
+            name "Alice"
+            email "alice@example.com"
+          end
+        end
+      RUBY
+
+      described_class.generate(fixtures_file: fixtures_file, output_dir: output_dir)
+
+      expect(File.exist?(File.join(output_dir, "users.yml"))).to be true
+      expect(File.exist?(File.join(output_dir, "posts.yml"))).to be false
+    end
+  end
+
+  it "returns early when fixtures file does not exist" do
+    Dir.mktmpdir do |tmpdir|
+      output_dir = File.join(tmpdir, "fixtures")
+
+      described_class.generate(
+        fixtures_file: File.join(tmpdir, "nonexistent.rb"),
+        output_dir: output_dir
+      )
+
+      expect(Dir.exist?(output_dir)).to be false
+    end
+  end
+end

spec/fixturebot/rails/generate_spec.rb

@@ -121,6 +121,19 @@
       expect(result.tables[:users][:admin][:email]).to eq("brad@blog.test")
     end
 
+    it "preserves explicit nil over generator" do
+      result = FixtureBot.define(schema) do
+        user.email { "#{name}@blog.test" }
+
+        user :admin do
+          name "Brad"
+          email nil
+        end
+      end
+
+      expect(result.tables[:users][:admin][:email]).to be_nil
+    end
+
     it "uses record_name as default name" do
       result = FixtureBot.define(schema) do
         user.email { "#{name}@blog.test" }