```ruby
require 'tmpdir'
require_relative '../../lib/yomou/blacklist'

class BlacklistTest < Test::Unit::TestCase
  setup do
  end

  sub_test_case "directory" do
    def test_directory
      Dir.mktmpdir do |dir|
        ENV['YOMOU_HOME'] = File.join(dir, '.yomou')
        path = File.join(ENV['YOMOU_HOME'], 'blacklist.yaml')
        blacklist = Yomou::Blacklist.new
        blacklist.init
        assert_equal(true, File.exist?(path))
      end
    end
  end
end
```

Add merge test for blacklist
user
```ruby
require 'tmpdir'
require_relative '../../lib/yomou/blacklist'

class BlacklistTest < Test::Unit::TestCase
  setup do
    @empty_ncodes = {
      'ncodes' => [
        'n12345'
      ]
    }
    @deleted_database = {
      1 => {
        'id' => 1,
        'toc_url' => 'http://ncode.syosetu.com/n98765/',
        'tags' => [
          '404'
        ]
      }
    }
  end

  sub_test_case "directory" do
    def test_directory
      Dir.mktmpdir do |dir|
        ENV['YOMOU_HOME'] = File.join(dir, '.yomou')
        path = File.join(ENV['YOMOU_HOME'], 'blacklist.yaml')
        blacklist = Yomou::Blacklist.new
        blacklist.init
        assert_equal(true, File.exist?(path))
      end
    end
  end

  sub_test_case "merge ncodes" do
    def test_merge_ncode
      Dir.mktmpdir do |dir|
        ENV['YOMOU_HOME'] = File.join(dir, '.yomou')
        save_to_yaml(blacklist_path, @empty_ncodes)
        blacklist = Yomou::Blacklist.new
        blacklist.init
        save_to_yaml(database_path('narou/00/.narou'), @deleted_database)
        blacklist.import
        expected = {
          'ncodes' => [
            'n12345', 'n98765'
          ]
        }
        assert_equal(expected, YAML.load_file(blacklist_path))
      end
    end
  end

  private
  def blacklist_path
    File.join(ENV['YOMOU_HOME'], 'blacklist.yaml')
  end

  def database_path(relative_path)
    path = File.join(ENV['YOMOU_HOME'], relative_path, 'database.yaml')
    FileUtils.mkdir_p(File.dirname(path))
    path
  end

  def save_to_yaml(path, data)
    FileUtils.mkdir_p(ENV['YOMOU_HOME'])
    File.open(path, 'w+') do |file|
      file.puts(YAML.dump(data))
    end
  end
end
```
assistant