Rails，minitest：如何测试控制器的输出

Question

My controller looks like this:

class CalculatorController < ApplicationController

  def calculate
    money = params[:money].to_f
   @worktime =  divide(money, 25)
  end

  private

  def divide(money, worktime)
    output = money/worktime
  end
end

I wrote a Test like this:

require 'test_helper'

class CalculatorControllerTest < ActionDispatch::IntegrationTest
  test "response" do
    get calculate_path
    assert_equal 200, response.status
  end
end

This test passes. Now, I want to write a test, to check, whether the output is correct. I tried this:

require 'test_helper'

class CalculatorControllerTest < ActionDispatch::IntegrationTest
  test "response" do
    get calculate_path(money: 25)
    assert_equal 200, response.status
    assert_equal 1, @response.worktime
  end
end

But this error occurs: NoMethodError: undefined method worktime'`

How do I test the output of the controller? ( In my case @worktime)

Answer 1

There's a good writeup here on the changes to testing in Rails 5: http://blog.bigbinary.com/2016/04/19/changes-to-test-controllers-in-rails-5.html

In Rails 4, you would use "assigns" to check that:

assert_equal 1, assigns(:worktime)

You can still have this functionality by including the rails-controller-testing gem https://github.com/rails/rails-controller-testing in your Gemfile in the test group. More here from dhh:

https://github.com/rails/rails/issues/18950

Answer 2

In Ruby @variables are instance variables. Not globals. Instance variables are always private*.

So @worktime is an instance variable that belongs to CalculatorController - not CalculatorControllerTest .

Ruby lets you access an instance variable without declaring it.

So this example:

require 'test_helper'

class CalculatorControllerTest < ActionDispatch::IntegrationTest
  test "response" do
    get calculate_path(money: 25)
    assert_equal 200, response.status
    assert_equal 1, @response.worktime
  end
end

Is actually in practice:

require 'test_helper'

class CalculatorControllerTest < ActionDispatch::IntegrationTest
  test "response" do
    get calculate_path(money: 25)
    assert_equal 200, response.status
    assert_equal 1, nil.worktime # since @worktime is not declared in this scope.
  end
end 

Previously you could pry into the inner workings of the controller with assigns which was removed in Rails 5. You can restore it with a gem but for new applications you should use a different approach to testing - you should instead test your controllers by testing the actual output in terms of response codes and JSON or HTML output. Not how it does its job.

require 'test_helper'

class CalculatorControllerTest < ActionDispatch::IntegrationTest
  test "response" do
    get calculate_path(money: 25)
    assert_equal 200, response.status
    assert_select "#result", "1"
  end
end