Ruby Language Pure RSpec JSON API testing Testing Serializer object and introducing it to Controller
Example
Let say you want to build your API to comply jsonapi.org specification and the result should look like:
{
"article": {
"id": "305",
"type": "articles",
"attributes": {
"title": "Asking Alexandria"
}
}
}
Test for Serializer object may look like this:
# spec/serializers/article_serializer_spec.rb
require 'rails_helper'
RSpec.describe ArticleSerializer do
subject { described_class.new(article) }
let(:article) { instance_double(Article, id: 678, title: "Bring Me The Horizon") }
describe "#as_json" do
let(:result) { subject.as_json }
it 'root should be article Hash' do
expect(result).to match({
article: be_kind_of(Hash)
})
end
context 'article hash' do
let(:article_hash) { result.fetch(:article) }
it 'should contain type and id' do
expect(article_hash).to match({
id: article.id.to_s,
type: 'articles',
attributes: be_kind_of(Hash)
})
end
context 'attributes' do
let(:article_hash_attributes) { article_hash.fetch(:attributes) }
it do
expect(article_hash_attributes).to match({
title: /[Hh]orizon/,
})
end
end
end
end
end
Serializer object may look like this:
# app/serializers/article_serializer.rb
class ArticleSerializer
attr_reader :article
def initialize(article)
@article = article
end
def as_json
{
article: {
id: article.id.to_s,
type: 'articles',
attributes: {
title: article.title
}
}
}
end
end
When we run our "serializers" specs everything passes.
That's pretty boring. Let's introduce a
typo to our Article Serializer: Instead of type: "articles" let's return type: "events" and rerun our tests.
rspec spec/serializers/article_serializer_spec.rb
.F.
Failures:
1) ArticleSerializer#as_json article hash should contain type and id
Failure/Error:
expect(article_hash).to match({
id: article.id.to_s,
type: 'articles',
attributes: be_kind_of(Hash)
})
expected {:id=>"678", :type=>"event",
:attributes=>{:title=>"Bring Me The Horizon"}} to match {:id=>"678",
:type=>"articles", :attributes=>(be a kind of Hash)}
Diff:
@@ -1,4 +1,4 @@
-:attributes => (be a kind of Hash),
+:attributes => {:title=>"Bring Me The Horizon"},
:id => "678",
-:type => "articles",
+:type => "events",
# ./spec/serializers/article_serializer_spec.rb:20:in `block (4
levels) in <top (required)>'
Once you've run the test it's pretty easy to spot the error.
Once you fix the error (correct the type to be article) you can introduce it to Controller like this:
# app/controllers/v2/articles_controller.rb
module V2
class ArticlesController < ApplicationController
def show
render json: serializer.as_json
end
private
def article
@article ||= Article.find(params[:id])
end
def serializer
@serializer ||= ArticleSerializer.new(article)
end
end
end
This example is based on article: http://www.eq8.eu/blogs/30-pure-rspec-json-api-testing
