【Rails】gem 'better_errors'を削除前後でテスト結果が異なる

Question

症状

Rails 5.0.2です。タイトル通りなのですが、
gem 'better_errors'を利用時、テストを行うと、

66/66: [===================================================================================================================================] 100% Time: 00:00:09, Time: 00:00:09

Finished in 10.01715s
66 tests, 237 assertions, 0 failures, 0 errors, 0 skips

しっかりテストが通るのですが、一方でGemfileから

 gem 'better_errors' 

を削除し、

$ bundle install

をします。その後、

$ rails test

を行うと

ERROR["test_フォロー", FollowingTest, 9.163654325999914]
 test_フォロー#FollowingTest (9.16s)
NoMethodError:         NoMethodError: undefined method `user_host_host_url' for #<User::RelationshipsController:0x007f8a7e6612b8>
        Did you mean?  user_host_url
                       user_hosts_url
            app/controllers/user/relationships_controller.rb:9:in `block (2 levels) in create'
            app/controllers/user/relationships_controller.rb:8:in `create'
            test/integration/following_test.rb:24:in `block (2 levels) in <class:FollowingTest>'
            test/integration/following_test.rb:23:in `block in <class:FollowingTest>'

ERROR["test_フォロー解除", FollowingTest, 9.32458399099994]
 test_フォロー解除#FollowingTest (9.32s)
NoMethodError:         NoMethodError: undefined method `user_host_host_url' for #<User::RelationshipsController:0x007f8a7e2646b0>
        Did you mean?  user_host_url
                       user_hosts_url
            app/controllers/user/relationships_controller.rb:19:in `block (2 levels) in destroy'
            app/controllers/user/relationships_controller.rb:18:in `destroy'
            test/integration/following_test.rb:38:in `block (2 levels) in <class:FollowingTest>'
            test/integration/following_test.rb:37:in `block in <class:FollowingTest>'

ERROR["test_フォロー(Ajax)", FollowingTest, 9.491528167999945]
 test_フォロー(Ajax)#FollowingTest (9.49s)
ActionView::Template::Error:         ActionView::Template::Error: undefined method `followers' for nil:NilClass
            app/views/user/relationships/create.js.erb:3:in `_app_views_user_relationships_create_js_erb___2393907348688590802_70116398321340'
            test/integration/following_test.rb:30:in `block (2 levels) in <class:FollowingTest>'
            test/integration/following_test.rb:29:in `block in <class:FollowingTest>'

  66/66: [===================================================================================================================================] 100% Time: 00:00:09, Time: 00:00:09

Finished in 9.80524s
66 tests, 234 assertions, 0 failures, 3 errors, 0 skips

このようにエラーが出ます。

今後ゆっくりテストがパスするよう頑張るつもりですが、
どうして、better_errors削除前後でテスト結果が変わるのかがさっぱりです。

個別エラーの意味というより、better_errors削除前後でのテスト仕様(？) について
もし情報をお持ちの方、ご助言頂けるとと幸いです。宜しくお願いします。

テストのファイル内容

念のため、記載します。

require 'test_helper'

class FollowingTest < ActionDispatch::IntegrationTest

	def setup
	  @user = users(:michael)
		@host = hosts(:google)
		log_in_as(@user)
	end

	test "フォローリストページ" do
	  get following_user_mypage_path
		assert_not   @user.following.empty?
		assert_match @user.following.count.to_s,response.body
		@user.following.each do |host|
			assert_select "a[href=?]",user_host_path(host)
		end
	end

	test "フォロー" do
	  assert_difference '@user.following.count',1 do   
			post user_relationships_path, params: { followed_id: @host.id }
	  end
	end

	test "フォロー(Ajax)" do
	  assert_difference '@user.following.count',1 do
	  	post user_relationships_path, params: { followed_id: @host.id }, xhr: true
	  end
	end

	test "フォロー解除" do
		@user.follow(@host)
		relationship = @user.active_relationships.find_by(followed_id: @host.id)
		assert_difference '@user.following.count', -1 do
			delete user_relationship_path(relationship)
		end
	end

	test "フォロー解除(Ajax)" do
	  @user.follow(@host)
		relationship = @user.active_relationships.find_by(followed_id: @host.id)
		assert_difference '@user.following.count', -1 do
			delete user_relationship_path(relationship),xhr:true
		end
	end

end