Rspec コントローラ、indexアクションのインスタンス変数@postsのテストでassigns(:posts)の中身が空の配列になっておりテストがうまく通らない。

posts_controllerのindexアクションのインスタンス変数@postsのテストを行なっています。
しかし、assigns(:posts)で上手く値を渡せず？中身が空の配列になっておりテストが通りません。
初歩的なことかもしれませんが何が起きているかさっぱりわからず困っています。
何か心当たりなどありましたらご教授お願いいたします。

現在の状態でテストを走らせると表示されるエラーメッセージ

1) PostsController#index created_at ascで並べ替えられたpostの配列
     Failure/Error: expect(assigns(:posts)).to match(posts.sort{|a, b| a.created_at <=> b.created_at })
     
       expected #<ActiveRecord::Relation []> to match [#<Post id: 235, title: "松田", address: "東京駅", image: "sample_image.jpg", content: "aaaaaaaaaaaaaaa", user_id: 347, created_at: "2020-01-05 20:52:44", updated_at: "2020-01-07 17:44:33", latitude: 35.6806303, longitude: 139.7687578>, #<Post id: 233, title: "杉山", address: "東京駅", image: "sample_image.jpg", content: "aaaaaaaaaaaaaaa", user_id: 345, created_at: "2020-01-05 22:52:05", updated_at: "2020-01-07 17:44:30", latitude: 35.6806303, longitude: 139.7687578>, #<Post id: 234, title: "池田", address: "東京駅", image: "sample_image.jpg", content: "aaaaaaaaaaaaaaa", user_id: 346, created_at: "2020-01-06 00:17:40", updated_at: "2020-01-07 17:44:32", latitude: 35.6806303, longitude: 139.7687578>]
       Diff:
       @@ -1,4 +1,2 @@
       -[#<Post id: 235, title: "松田", address: "東京駅", image: "sample_image.jpg", content: "aaaaaaaaaaaaaaa", user_id: 347, created_at: "2020-01-05 20:52:44", updated_at: "2020-01-07 17:44:33", latitude: 35.6806303, longitude: 139.7687578>,
       - #<Post id: 233, title: "杉山", address: "東京駅", image: "sample_image.jpg", content: "aaaaaaaaaaaaaaa", user_id: 345, created_at: "2020-01-05 22:52:05", updated_at: "2020-01-07 17:44:30", latitude: 35.6806303, longitude: 139.7687578>,
       - #<Post id: 234, title: "池田", address: "東京駅", image: "sample_image.jpg", content: "aaaaaaaaaaaaaaa", user_id: 346, created_at: "2020-01-06 00:17:40", updated_at: "2020-01-07 17:44:32", latitude: 35.6806303, longitude: 139.7687578>]
       +[]
       
     # ./spec/controllers/posts_controller_spec.rb:13:in `block (3 levels) in <top (required)>'

binding.pryでassigns(:posts)を確認

 8: 
     9:   describe '#index' do
    10: 
    11:       it "created_at ascで並べ替えられたpostの配列" do
    12:         get :index
 => 13:         binding.pry
    14:         expect(assigns(:posts)).to match_array posts
    15:       end
    16: 
    17:       
    18: 

[1] pry(#<RSpec::ExampleGroups::PostsController::Index>)> assigns(:posts)
=> []

posts_controller_spec.rb

require 'rails_helper'

describe PostsController do

  let(:user) { create(:user) }
  let(:posts) { create_list(:post, 3) }
  

  describe '#index' do

      it "created_at ascで並べ替えられたpostの配列" do
        get :index
        expect(assigns(:posts)).to match(posts.sort{|a, b| a.created_at <=> b.created_at })
      end

      

  end

end

posts_controller.rb

def index
    @posts = Post.all.order("created_at asc").page(params[:page]).per(12)
end

spec/factories/posts.rb

FactoryBot.define do

  factory :post do
    title              {Faker::Name.last_name}
    address            {'東京駅'}
    image              { Rack::Test::UploadedFile.new(Rails.root.join('spec/support/sample_image.jpg'), 'image/jpeg') }
    content            {'aaaaaaaaaaaaaaa'}
    latitude           {35.6959}
    longitude          {139.702}
    created_at { Faker::Time.between(from: DateTime.now - 2, to: DateTime.now) }
    user
  end

end