How to test a polymorphic association on a controller with Minitest? - ruby-on-rails-4

Question

I am having trouble making a test pass for my posts controller.
What is the proper way to test my create action inside the Posts controller with a polymorphic association?
I'm using Rails 4
Here's my code
Models:
class Topic < ActiveRecord::Base
belongs_to :user
belongs_to :category
has_many :posts, as: :postable
has_many :posts, dependent: :destroy
validates :name, presence: true, length: {maximum: 50}
validates :description, presence: true, length: {maximum: 80}
validates :user_id, presence: true
is_impressionable
end
class Post < ActiveRecord::Base
belongs_to :user
belongs_to :topic
belongs_to :category
belongs_to :postable, polymorphic: true
has_many :posts, as: :postable
validates :comment, presence: true
validates :user_id, presence: true
validates :topic_id, presence: true
validates :category_id, presence: true
default_scope { order(created_at: :asc) }
end
Post controller
class PostsController < ApplicationController
before_action :auth_user
before_action :set_post, only: [:destroy]
before_action :correct_user, only: [:destroy]
before_action :find_postable, only: [:create, :new]
def new
#post = #postable.posts.build
end
def create
#post = #postable.posts.build(post_params)
set_topic_id
set_category_id
#post.user_id = current_user.id
if #post.save
redirect_to topic_path(#post.topic.id)
else
redirect_to request.referer, notice: "Post unsuccessful!"
end
end
def destroy
#post.destroy
flash[:success] = 'Post deleted'
redirect_to request.referer || root_url
end
private
def set_post
#post = Post.find(params[:id])
end
def correct_user
#post = current_user.posts.find_by(id: params[:id])
redirect_to root_url if #post.nil?
end
def find_topic
#topic = Topic.find(params[:topic_id])
end
def find_postable
#postable = Post.find_by_id(params[:post_id]) if params[:post_id]
#postable = Topic.find_by_id(params[:topic_id]) if
params[:topic_id]
end
def post_params
params.require(:post).permit(:comment)
end
end
Post controller test:
require 'test_helper'
class PostsControllerTest < ActionController::TestCase
def setup
#topic = topics(:topicone)
#post = posts(:postone)
#posttwo = posts(:posttwo)
#category = categories(:categoryone)
#user = users(:user1)
end
test 'should create post when logged in' do
sign_in #user
assert_difference 'Post.count', 1 do
post :create, post: { user_id: #user.id, category_id:
#category.id, topic_id: #topic.id, comment: "First reply!",
postable_id: #post.id, postable_type: "Post" }
end
end
end
When I run the test above I get this error:
ERROR["test_should_create_post_when_logged_in", PostsControllerTest,
2016-12-04 14:23:25 -0500]
test_should_create_post_when_logged_in#PostsControllerTest
(1480879405.93s)
NoMethodError: NoMethodError: undefined method `posts' for nil:NilClass
app/controllers/posts_controller.rb:13:in `create'
test/controllers/posts_controller_test.rb:28:in `block (2
levels) in <class:PostsControllerTest>'
test/controllers/posts_controller_test.rb:25:in `block in
<class:PostsControllerTest>'
app/controllers/posts_controller.rb:13:in `create'
test/controllers/posts_controller_test.rb:28:in `block (2 levels)
in <class:PostsControllerTest>'
test/controllers/posts_controller_test.rb:25:in `block in
<class:PostsControllerTest>'
From my understanding, I believe it's telling me that it can't find whether the create action is posting to a post or to a topic.
The site works great in development and production. The problem is in this test.
How can I rewrite this test and make it so it recognizes to whom it's posting to?

Answer 1

I found a solution for this shortly after.
In this case, to successfully test if a post is created on a topic, make sure to provide the topic_id.
test 'should create post on a topic when logged in' do
sign_in #user
assert_difference 'Post.count', 1 do
post :create, topic_id: #topic, post: {
user_id: #user.id,
category_id: #category.id,
comment: 'First post on a topic!' }
end
end
Now to test if a post is created on another post, make sure to provide the post_id.
test 'should create post on another post when logged in' do
sign_in #user
assert_difference 'Post.count', 1 do
post :create, post_id: #post, post: {
user_id: #user.id,
category_id: #category.id,
comment: 'First post on a topic!' }
end
end