how to test carrierwave fog google in rspec with setting up the configuration

I have below configuration and I wanted to write TC for it in ruby. I am new to ruby and wanted to understand how we can set the configuration of Fog to point to mock and use it in test-case.

class TestUploader < CarrierWave::Uploader::Base

  storage :fog

  def fog_credentials
    {
      :provider => 'google',
      :google_project =>'my project',
      :google_json_key_location =>'myCredentialFile.json'

    }
  end


  def fog_provider
    'fog/google'
  end

  def fog_directory
    '{#bucket-name}'
  end

  def store_dir

    when :File
      "#{file.getpath}/file"
    when :audio
      "#{file.getpath}/audio"
    else
      p " Invalid file "
    end
  end
end

class TestModel

  mount_uploader :images, TestUploader

end

Could someone please assist me from configuring to write and execute the unit test on it with few example. Any help would be really appreciated.