Rspec let变量不是Mailer的参数

Question

在我的测试中，Rpec，我有这个

   before { @user = create(:user) }
   let(:mail) { SignUpMailer.message(@user) }

然后我收到错误：

 Failure/Error: @mail = SignUpMailer.message(@user) }
     ArgumentError:
       wrong number of arguments (0 for 1)

我也尝试过：

before { @user = create(:user)
         @mail = SignUpMailer.message(@user) }

但它仍然说上面的错误。有什么想法吗？

修改 邮件代码

class SignUpMailer < ActionMailer::Base
  default from: "Assign It App <support@assignitapp.com>"

      # Subject can be set in your I18n file at config/locales/en.yml
      # with the following lookup:
      #
      #   en.sign_up_mailer.message.subject
      #
      def message(user)
        @sign_in_url = sign_in_url
        @user_name = user.name
        mail subject: "Welcome to Assign It App"
        mail to: user.email
      end
    end

另一项尝试：

before { @user = create(:user) }
let(:mail) { SignUpMailer.message([@user]) }

哪个给我

 Failure/Error: let(:mail) { SignUpMailer.message([@user]) }
     NoMethodError:
       undefined method `name' for #<Array:0xa0c9860>

所以邮件确实接受了争论。