Rails密码重置邮件程序测试未定义方法“html_safe”错误(使用Clearance gem)

我试图在Rails中创建一个邮件程序测试,以检查密码重置邮件程序 Clearance sends .

密码重置邮件程序的默认视图中有以下链接:

<%= link_to "Change my password",
    edit_user_password_url(@user, token: @user.confirmation_token.html_safe) %>

好像在打电话 html_safe 这是一件好事,但在我的邮件程序测试中,我一直收到这个错误:

Minitest::UnexpectedError: ActionView::Template::Error: undefined method `html_safe' for nil:NilClass
Did you mean?  html_safe?

我不明白为什么会发生这种情况。这是我到目前为止的邮件测试:

require "test_helper"

class PasswordResetMailerTest < ActionMailer::TestCase
  setup do
    @user = users(:elvis)
  end

  test "password reset email" do
    email = ClearanceMailer.change_password(@user)

    # Send the email, then test that it got queued
    assert_emails 1 do
      email.deliver_now
    end
  end
end

为什么这会导致 undefined method html_safe 错误?