Run in CI: RAILS_ENV=test bundle exec rails db:seed_fu:lint

seed_fu.rake

# lib/tasks/seed_fu/lint.rake
namespace :db do
  namespace :seed_fu do
    desc 'Verify that all fixtures are valid'
    task lint: :environment do
      if Rails.env.test?
        conn = ActiveRecord::Base.connection

        %w[development test production].each do |env|
          conn.transaction do
            SeedFu.seed("db/fixtures/#{env}")
            raise ActiveRecord::Rollback
          end
        end
      else
        system("bundle exec rails db:seed_fu:lint RAILS_ENV='test'")
        fail if $?.exitstatus.nonzero?
      end
    end
  end
end