```ruby
require "shrine/storage/memory"
require "dry-initializer"

module Support
  module ShrineHelper
    def shrine(&block)
      uploader_class = Class.new(Shrine)
      uploader_class.storages[:cache]       = Shrine::Storage::Memory.new
      uploader_class.storages[:other_cache] = Shrine::Storage::Memory.new
      uploader_class.storages[:store]       = Shrine::Storage::Memory.new
      uploader_class.storages[:other_store] = Shrine::Storage::Memory.new
      uploader_class.class_eval(&block) if block
      uploader_class
    end

    def uploader(storage_key = :store, &block)
      uploader_class = shrine(&block)
      uploader_class.new(storage_key)
    end

    def attacher(**options, &block)
      shrine = shrine(&block)
      shrine::Attacher.new(**options)
    end

    def model_class(*attributes)
      klass = entity_class(*attributes)
      klass.attr_writer *attributes
      klass
    end

    def entity_class(*attributes)
      klass = Class.new
      klass.extend Dry::Initializer
      attributes.each do |attribute|
        klass.option attribute, optional: true
      end
      klass
    end

    def struct(attributes)
      struct_class = entity_class(*attributes.keys)
      struct_class.new(attributes)
    end
  end
end

Minitest::Test.include Support::ShrineHelper
```

Fix tests on MRI 2.3 and 2.4
user
```ruby
require "shrine/storage/memory"
require "dry-initializer"

module Support
  module ShrineHelper
    def shrine(&block)
      uploader_class = Class.new(Shrine)
      uploader_class.storages[:cache]       = Shrine::Storage::Memory.new
      uploader_class.storages[:other_cache] = Shrine::Storage::Memory.new
      uploader_class.storages[:store]       = Shrine::Storage::Memory.new
      uploader_class.storages[:other_store] = Shrine::Storage::Memory.new
      uploader_class.class_eval(&block) if block
      uploader_class
    end

    def uploader(storage_key = :store, &block)
      uploader_class = shrine(&block)
      uploader_class.new(storage_key)
    end

    def attacher(**options, &block)
      shrine = shrine(&block)
      shrine::Attacher.new(**options)
    end

    def model_class(*attributes)
      klass = entity_class(*attributes)
      klass.send(:attr_writer, *attributes)
      klass
    end

    def entity_class(*attributes)
      klass = Class.new
      klass.extend Dry::Initializer
      attributes.each do |attribute|
        klass.option attribute, optional: true
      end
      klass
    end

    def struct(attributes)
      struct_class = entity_class(*attributes.keys)
      struct_class.new(attributes)
    end
  end
end

Minitest::Test.include Support::ShrineHelper
```
assistant