Rails 5 default_url_options oddities

I have a fairly simple rails app that I am working on upgrading from Rails 4 to Rails 5, but I am noticing something strange with default_url_options

In config/environments/test.rb

I have:

Rails.application.routes.default_url_options[:host]= ENV["HTTP_HOST"] || "localhost"
Rails.application.routes.default_url_options[:port]= ENV["PORT"] || 3000

      

        
        
        
      

    

My application has a namespace api

. In my request specs, I see this:

[1] pry> api_v3_sample_url
=> "http://www.example.com:3000/api/v3/sample"
[2] pry> Rails.application.routes.url_helpers.api_v3_sample_url
=> "http://localhost:3000/api/v3/sample"

      

        
        
        
      

    

What am I missing because these urls are different?

EDIT

Per this thread I have installed

config.action_controller.default_url_options = {
  host: ENV['HTTP_HOST'] || 'localhost'
}

      

        
        
        
      

    

in config/environments/test.rb

, but now I get this:

> Rails.application.routes.url_helpers.api_v3_sample_url
ArgumentError: Missing host to link to! Please provide the :host parameter, set default_url_options[:host], or set :only_path to true
> api_v3_sample_url
=> "http://www.example.com/api/v3/sample"

      

        
        
        
      

    

EDIT 2

It might be worth noting that these are request specs, not spec specs (not using capybara).