How to generate fixtures based on my development database?

I'm lazy and I since my production database has data I could use for testing through on going developm开发者_StackOverflow中文版ent, I was wondering if there were any easy methods of generating fixtures.

---

The question is old, but as it still seems relevant: yes, there is an easy way to create fixtures from your development database:

class ActiveRecord::Base
  def dump_fixture
    fixture_file = "#{Rails.root}/test/fixtures/#{self.class.table_name}.yml"
    File.open(fixture_file, "a+") do |f|
      f.puts({ "#{self.class.table_name.singularize}_#{id}" => attributes }.
        to_yaml.sub!(/---\s?/, "\n"))
    end
  end
end

Place this in a file in config/initializers - now you can dump any ActiveRecord object in your Rails console and it will automatically be appended at the end of it's respective fixture file:

User.first.dump_fixture appends fixture data to test/fixtures/users.yml.

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In case you're creating a script to run under rails runner you can use the following approach:

File.open("#{Rails.root}/spec/fixtures/documents.yml", 'w') do |file|
  file.write Document.all.to_a.map(&:attributes).to_yaml
end

you can create as much blocks as you want, or if you want to go to the full database you can try:

models = defined?(AppicationRecord) ? ApplicationRecord.decendants : ActiveRecord::Base.descendants
models.each do |model|
  model_name = model.name.pluralize.underscore
  File.open("#{Rails.root}/spec/fixtures/#{model_name}.yml", 'w') do |file|
    file.write model.all.to_a.map(&:attributes).to_yaml
  end
end

if you do not want the timestamps you can change the code to: model.all.to_a.map { |m| m.attributes.except('created_at', 'updated_at')}.to_yaml

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Building on @nikolasgd's answer I wrote a Rake Task, which may be useful for some:

# Use like "rake custom:create_test_fixtures[model]"
namespace :custom do
  desc 'Re-Creates Fixtures for Testing for a Model'

  task :create_test_fixtures, [:model] => [:environment] do |t, args|
    class ActiveRecord::Base
      def dump_fixture
        fixture_file = "#{Rails.root}/test/fixtures/#{self.class.table_name}.yml"
        File.open(fixture_file, "a+") do |f|
          f.puts({"#{self.class.table_name.singularize}_#{id}" => attributes}.
              to_yaml.sub!(/---\s?/, "\n"))
        end
      end
    end

    begin
      model = args[:model].constantize
      model.all.map(&:dump_fixture)
      puts "OK: Created Fixture for Model \"#{args[:model]}\"."
    rescue NameError
      puts "ERROR: Model \"#{args[:model]}\" not found."
    end

  end
end

---

I expanded the solution by @nikolasgd to also support ActiveStorage attachment fields/blobs and support naming dumped objects:

# config/initializers/generate_fixture.rb
class ActiveRecord::Base

  # Append this record to the fixture.yml for this record class
  def dump_fixture(name: nil, include_attachments: false)

    # puts "Dumping fixture for #{self.class.name} id=#{id} #{"with name #{name}" if name}"

    attributes_to_exclude = [:updated_at, :created_at, *Rails.application.config.filter_parameters].map(&:to_s)
    attributes_to_exclude << "id" if name != nil

    # puts "  Attributes excluded: #{attributes_to_exclude.inspect}"

    attributes_to_dump = attributes
      .except(*attributes_to_exclude)
      .reject { |k,v| v.blank? }

    name = "#{self.class.table_name.singularize}_#{id}" if name == nil

    self.dump_raw_fixture({ name => attributes_to_dump }.to_yaml.sub(/---\s?/, "\n"))

    if include_attachments != false
      self.class.reflect_on_all_attachments
        .each { |association|

          a_name = association.name
          Array(self.send(a_name.to_sym)).each_with_index { |attachment, index|

            attachment_name = "#{name}_#{a_name.to_s.underscore}_#{index}"
            blob_name = "#{attachment_name}_blob"

            attachment.dump_raw_fixture({ name => {
              "name" => a_name,
              "record" => "#{name} (#{self.class.name})",
              "blob" => blob_name
            }}.to_yaml.sub(/---\s?/, "\n"))

            blob = attachment.blob
            blob.dump_raw_fixture("#{blob_name}: <%= ActiveStorage::Blob.fixture(filename: '#{blob.filename}') %>\n")
            blob_path = "#{Rails.root}/test/fixtures/files/#{blob.filename}"
            File.open(blob_path, "wb+") do |file|
              blob.download { |chunk| file.write(chunk) }
            end
          }
        }
    end
  end

  def dump_raw_fixture(text)
    fixture_file = "#{Rails.root}/test/fixtures/#{self.class.name.underscore.pluralize}.yml"
    File.open(fixture_file, "a+") do |f|
      f.puts(text)
    end
  end

end

It requires the following test_helper (Rails 7 will obsolete this):

# test/test_helper.rb
class ActiveStorage::Blob
  def self.fixture(filename:, **attributes)
    blob = new(
      filename: filename,
      key: generate_unique_secure_token
    )
    io = Rails.root.join("test/fixtures/files/#{filename}").open
    blob.unfurl(io)
    blob.assign_attributes(attributes)
    blob.upload_without_unfurling(io)

    blob.attributes.transform_values { |values| values.is_a?(Hash) ? values.to_json : values }.compact.to_json
  end
end

You can run this from rails console as before:

User.find(1).dump_fixture name: bob, include_attachments: true