Rspec let variable isn't an argument for a Mailer
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In my Test, Rpec, I have this

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

Then I get an error of:

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

I have also tried:

    before { @user = create(:user)
             @mail = SignUpMailer.message(@user) }
But it still says the error above. Any thoughts?
