demarches-normaliennes/spec/mailers/previews/user_mailer_preview.rb

class UserMailerPreview < ActionMailer::Preview
  def new_account_warning
    UserMailer.new_account_warning(user)
  end

  def account_already_taken
    UserMailer.account_already_taken(user, 'dircab@territoires.gouv.fr')
  end

  private

  def user
    User.new(id: 10, email: 'test@exemple.fr')
  end
end