我在使用stubs时遇到了问题，并且不确定应该如何测试这个类方法：

class Artist < ActiveRecord::Base
  def self.import(file)
    CSV.foreach(file.path, headers: true) do |row|
      Artist.find_or_create_by(row.to_hash)
    end
  end
end

RSpec.describe Artist, type: :model do
  describe ".import" do
    before :each do
      create(:artist, name: 'artist1', facebook_url: nil)
      create(:artist, name: 'artist2', facebook_url: "facebook_url")
    end

    context "when facebook_url is empty" do
      it "updates facebook_url" do
        #Here I should somehow stub CSV with name, facebook_url
        #headers and row: artist1,artist1_facebook_url - HOW ?

        Artist.import(file)
        expect(Artist.find_by(name: 'artist1').facebook_url).to eq "artist1_facebook_url"
      end
    end
  end
end

我应该如何存根它使这个测试工作？