test missing template - ruby-on-rails

Question

Trying to write what should be a straightforward RSpec test and have set up my create action to render JSON like the following:
require 'spec_helper'
describe CommentsController do
let(:valid_attributes) do
{
title: 'First Comment', comment_text: 'LoremIpsum', commentable_id: 1,
user_id: 1, entered_by: 'john', last_updated_by: 'doe'
}
end
context 'JSON' do
describe 'POST create' do
describe 'with valid params' do
it 'creates a new Comment' do
json = {:format => 'json', :comment => valid_attributes}
post :create, json
end
it 'assigns a newly created comment as #comment' do
json = {:format => 'json', :comment => valid_attributes}
post :create, json
assigns(:comment).should be_a(Comment)
assigns(:comment).should be_persisted
end
end
end
end
end
However I am getting the following output:
ActionView::MissingTemplate: Missing template comments/create, application/create with {:locale=>[:en], :formats=>[:json], :handlers=>[:erb, :builder, :raw, :ruby, :jbuilder, :coffee, :haml]}. Searched in:

Answer 1

you missed the else part when #commentable is nil. this will try rendering the default template!
to clarify:
this is what was posted initially:
def create
if #commentable
#comment = #commentable.comments.new(comment_params)
if #comment.save
render json: #comment, status: :created
else
render json: #comment.errors, status: :unprocessable_entity
end
end
end
in the case where #commentable is nil there is nothing that tells rails what to render, so it will try to render the default template for the create action. this is where Missing template comments/create comes from.
what i mean with the else part is this:
def create
if #commentable
[...]
else
head 404
end
end