Rails Anonymous Controller Testing

I sometimes want to test an abstract controller, a controller concern, a view, or a helper method.

This might be useful for you if you're working on a Rails engine or if you're editing your ApplicationController.

This only works with Minitest, specifically for tests that inherit from ActionDispatch::IntegrationTest.

Here's a relatively straightforward example. There are a few caveats you might need to keep in mind for more complicated cases; see the Caveats section below.

class MyControllerTest < ActionDispatch::IntegrationTest
  # 1. Call the `controller` method. You must specify the base controller to
  #    inherit from. It'll set up routes with `resources :anonymous`.
  controller(ApplicationController) do
    def index
    end

    def show
      render plain: params[:id]
    end
  end

  # 2. Optionally, set views. You can set the layout for your anonymous
  #    controller too.
  views["layouts/application.html.erb"] = <<~HTML
    <h1>My anonymous test</h1>
    <%= yield %>
  HTML

  views["index.html.erb"] = <<~HTML
    <h2>Hi</h2>
  HTML

  # 3. Test like it's a regular controller in your application
  def test_index
    get "/anonymous"
    assert_select "h1", "My anonymous test"
    assert_select "h2", "Hi"
  end

  def test_show
    get "/anonymous/1234"
    assert_equal "1234", response.body
  end
end

You can also specify the routes too, but you need to namespace the controller to the name of the test class.

class MyControllerTest < ActionDispatch::IntegrationTest
  routes = -> { get "custom", to: "my_controller_test/anonymous#custom" }
  controller(ApplicationController, routes: routes) do
    def custom
    end
  end
end

A few things to note

• You can only define one controller do per test class. But you can get around this limitation by defining another test class in one file.
• Views are generated only once and cached. The cache key is determined by MD5 hashing the test file contents, and test file path, and the line number of the controller do.
• You can disable the view cache by calling disable_anonymous_view_cache! on your test class. This doesn't get around the limitation of having just one controller do definition in your test class.
• The view cache is located in tmp/anonymous_controller_views and can be cleared anytime
• Setting a custom layout will only affect your anonymous controller. This gem does not provide any way to affect the behavior of existing controllers defined by your Rails application or engine

Add this line to your application's Gemfile:

gem "rails_anonymous_controller_testing", group: :test

And then execute:

$ bundle

Contributions very welcome. Please give me edit access to your branch for a faster turnaround.

The gem is available as open source under the terms of the MIT License.