describe 'nested attributes on articles (which has_many comments)' do  before do    @hash = {      "article" => {        "title" => "Test",        "body" => "test body",        "comments_attributes" => {          '0'=>{"author" => "John", "content" => "great"},          '1'=>{"author" => "Mary", "content" => "awful"}        }      }    }    @params = ActionController::Parameters.new @hash  end  it 'shows how to permit nested parameters' do    attributes = @params.      require(:article).      permit(:title, comments_attributes: [:author,                                :content])[:comments_attributes].        must_equal @hash['article']['comments_attributes']  endend

http://www.carreno.me/articles/understanding-strong-parameters-in-rails-4