controller_params_test.rb

require 'bundler/inline'

gemfile do
  source 'https://rubygems.org'

  gem 'rails', '5.1.6'
end

require 'action_controller/railtie'
require 'minitest/autorun'
require 'rails/test_help'

class TestApp < Rails::Application
  secrets.secret_key_base = 'secret_key_base'

  ::Rails.logger = ::Logger.new(nil)

  routes.draw do
    get '/' => 'test#index'
  end
end

class TestController < ActionController::Base
  include ::Rails.application.routes.url_helpers

  def index
    head(200)
  end
end

class ControllerParamsTest < ActionController::TestCase
  def setup
    super
    @controller = ::TestController.new
  end

  def test_params_with_empty_hash
    get :index, params: {}
    assert_equal 200, response.status
  end

  def test_params_with_nil
    get :index, params: nil
    assert_equal 200, response.status
  end
end

Expected

$ ruby controller_params_test.rb
Run options: --seed 8188

# Running:

..

Finished in 0.069279s, 28.8688 runs/s, 28.8688 assertions/s.
2 runs, 2 assertions, 0 failures, 0 errors, 0 skips

Actual

$ ruby controller_params_test.rb
Run options: --seed 46396

# Running:

.E

Error:
ControllerParamsTest#test_params_with_nil:
NoMethodError: undefined method `symbolize_keys' for nil:NilClass



bin/rails test controller_params_test.rb:43



Finished in 0.065820s, 30.3859 runs/s, 15.1930 assertions/s.
2 runs, 1 assertions, 0 failures, 1 errors, 0 skips