Rails Testing Controller index action Error

I am getting an error running rails test that says:

ActionView::Template::Error:         
ActionView::Template::Error: No route matches {:action=>"show", :controller=>"users", :format=>nil, :id=>nil}, possible unmatched constraints: [:id]
        app/views/children/index.html.erb:77:in `_app_views_children_index_html_erb___4404788417012424682_71382320'
        test/controllers/children_controller_test.rb:9:in `block in <class:ChildrenControllerTest>'

test/controllers/children_controller_test.rb:

require 'test_helper'

class ChildrenControllerTest < ActionDispatch::IntegrationTest
setup do
 @child = children(:one)
end

test "should get index" do
 get children_url
 assert_response :success
end

app/views/children/index.html.erb:77:

<%= link_to "Zurück zum Profil", user_path(current_user), class: "btn btn-default btn-sm", "data-turbolinks": "false"   %>

Unfortunately I have no idea whats the problem there..

Help would be appreciated!