Ruby on Rails Rspec undefined method host error

Question

When I try to write test to a method in controller I received undefined method host error. Here is the example code blocks below

In rspec file:

require 'rails_helper'

RSpec.describe FooController, type: :controller do

 before do
      @controller = FooController.new
      @controller.params = ActionController::Parameters.new({ foo_id: foo.id, })


      @set_foo = @controller.send(:set_foo_data)

 end

and in foo controller:

def set_foo_data
  @foo_data = {
      table_type: :foo,
      .
      .
      data_url: foos_path,
  }
end

data_url part causing this issue.

I checked with byebug and data_url was nil.

Answer 1

The reason this doesn't work is that controllers are Rack middleware and expect to be initialized with a request. Its also just not how you should be coding or testing your code in the first place. Bin it.

Controller specs use the get, post, etc methods that actually create an instance of the controller with a mocked request.

get :foo would then call the foo method directly on the controller instance. You do not initialize controllers directly. If you feel tempted to do this its a very good sign you're doing something very wrong.

Unit testing controllers with controller specs is an extremely flawed approach that's discouraged by both the RSpec and Rails teams - you're mocking out huge parts of the application like the middleware and routes and it lets so many bugs through your tests.

The modern way to test a Rails application is to just test the actions of your controller by sending HTTP requests. This means that you should ONLY test the methods that actually correspond to a route and test your application through the response it provides (the headers and body) and eventually the side effects. In RSpec-Rails this is provided through request, feature and system specs.

Everything else in your controller like this method should be private - and you don't test privates.