Getting Answers to Your Testing Questions

Getting Answers to Your Testing Questions

Josh Justice

CodingItWrong

CodingItWrong

@bignerdranch bignerdranch.com

Ruby on Rails course June 27–July 1

bit.ly/nerdrails

How do I get started testing? 🤔

Questions! 🤔• Do I write the test or production code first?

• What do I test first?

• How many acceptance/unit tests do I write?

• How much test code do I write at a time? Production code?

• Do I test every line of code and configuration?

• How much do I use test doubles? What do I test for?

Everyone agrees! 🙈

"Unit tests are good!" "Unit tests are bad!" "Mocks are good!" "Mocks are bad!"

😩

What if we didn’t have to worry about all those

questions at once?

Test-Driven Development:

An approach to testing that provides a consistent set of answers to those questions.

“TDD is dead”…?

Too rigid?

• Not “follow this exactly or you’re a bad developer.”

• Not “this is the only way it can be done.”

• Give it a whole-hearted try. Then you’ll know when to apply it and when not to.

• Or, just take a principle or two and see if they help.

Goals

• Show TDD applied to a small real-world example.

• Show how it answers those questions about how to get started in testing.

• Motivate you to try it if you haven’t (or if you haven’t strictly).

Not Goals

• Convince you testing is a good idea.

• Introduce testing concepts and terms.

• Provide rationale for individual points of TDD.

learntdd.in/rails

Requirement: as a user, I want to be able to create a blog post.

(of course)

Do I write the test or production code first?

Write tests first.

🤔

Why tests first?

• To make sure there's time to test.

• To make sure your code is covered by tests.

• To make sure your code is easy to test.

• To let tests drive your design.

What do I test first?

Start outside the system.

🤔

How much test do I write at a time?

Write a whole acceptance test for one feature.

🤔

# spec/features/creating_a_blog_post_spec.rb require 'rails_helper'

describe 'Creating a blog post' do

it 'saves and displays the resulting blog post' do visit '/blog_posts/new'

fill_in 'Title', with: 'Hello, World!' fill_in 'Body', with: 'Hello, I say!'

click_on 'Create Blog Post'

blog_post = BlogPost.order("id").last expect(blog_post.title).to eq('Hello, World!') expect(blog_post.body).to eq('Hello, I say!')

expect(page).to have_content('Hello, World!') expect(page).to have_content('Hello, I say!') end

end








end How much do I use test doubles?

In acceptance tests, don’t use test doubles.

🤔

Run the test and watch it fail, to know what to

implement first.

# rspec spec/features/creating_a_blog_post_spec.rbF

Failures:

1) Creating a blog post saves and displays the resulting blog post Failure/Error: visit '/blog_posts/new'

ActionController::RoutingError: No route matches [GET] "/blog_posts/new"

# config/routes.rb Rails.application.routes.draw do resources :blog_posts end


Do I test every line?

No, you can fix trivial errors directly.

🤔


How much production code do I write at a time?

Just enough to fix the current error.

🤔

Red-Green-Refactor

A note on refactoring.


Failures:


ActionController::RoutingError: uninitialized constant BlogPostsController

# app/controllers/blog_posts_controller.rb class BlogPostsController < ApplicationController end


Failures:


AbstractController::ActionNotFound: The action 'new' could not be found for BlogPostsController

# app/controllers/blog_posts_controller.rb class BlogPostsController < ApplicationController def new end end


Failures:


ActionView::MissingTemplate: Missing template blog_posts/new

<%# app/views/blog_posts/new.html.erb %>


Failures:

1) Creating a blog post saves and displays the resulting blog post Failure/Error: fill_in 'Title', with: 'Hello, World!'

Capybara::ElementNotFound: Unable to find field "Title"

<%# app/views/blog_posts/new.html.erb %> <%= form_for @blog_post do |f| %> <div> <%= f.label :title %> <%= f.text_field :title %> </div> <div> <%= f.label :body %> <%= f.text_area :body %> </div> <%= f.submit 'Create Blog Post' %> <% end %>

<%# app/views/blog_posts/new.html.erb %> <%= form_for @blog_post do |f| %> <div> <%= f.label :title %> <%= f.text_field :title %> </div> <div> <%= f.label :body %> <%= f.text_area :body %> </div> <%= f.submit 'Create Blog Post' %> <% end %>

How much production code do I write at a time?

Sometimes, more than enough to fix the current error.

🤔


Failures:

1) Creating a blog post saves and displays the resulting blog post Failure/Error: <%= form_for @blog_post do |f| %>

ActionView::Template::Error: First argument in form cannot contain nil or be empty


Failures:

1) Creating a blog post saves and displays the resulting blog post Failure/Error: <%= form_for @blog_post do |f| %>

ActionView::Template::Error: First argument in form cannot contain nil or be empty

When do I write unit tests?

Step down to a unit test when there are behavioral errors.

🤔

Why unit test when there's already an acceptance test?

Acceptance tests demonstrate external quality: whether the

system works.

Acceptance tests don't demonstrate internal quality: whether the

code is maintainable.

Unit tests expose internal quality. They drive design.

# spec/controllers/blog_posts_controller_spec.rb require 'rails_helper'

describe BlogPostsController do

describe '#new' do it 'returns a blog post' do blog_post = instance_double(BlogPost) expect(BlogPost).to receive(:new).and_return(blog_post) get :new expect(assigns[:blog_post]).to eq(blog_post) end end

end




end How much test do I write?

Write only enough unit test to expose the behavioral error.

🤔




end How much test do I write?

Specify one behavior per unit test case.

🤔




end How much do I use test doubles?

In unit tests, use test doubles in place of any collaborators.

🤔




end What do I test for?

In unit tests, behavior, not state. (Mostly.)

🤔

# rspec spec/controllers/blog_posts_controller_spec.rbF

Failures:

1) BlogPostsController#new returns a blog post Failure/Error: blog_post = instance_double(BlogPost)

NameError: uninitialized constant BlogPost

# db/migrate/20160223100510_create_blog_posts.rb class CreateBlogPosts < ActiveRecord::Migration def change create_table :blog_posts do |t| t.string :title t.text :body end end end

# app/models/blog_post.rb class BlogPost < ActiveRecord::Base end

# rspec spec/controllers/blog_posts_controller_spec.rbF

Failures:

1) BlogPostsController#new returns a blog post Failure/Error: expect(assigns[:blog_post]).to eq(blog_post)

expected: #<InstanceDouble(BlogPost) (anonymous)> got: nil

(compared using ==)

# app/controllers/blog_posts_controller.rb class BlogPostsController < ApplicationController def new @blog_post = BlogPost.new end end

# rspec spec/controllers/blog_posts_controller_spec.rb.

Finished in 0.03134 seconds (files took 1.46 seconds to load)1 example, 0 failures

How often do I run which tests?

When the unit test passes, step back up to the acceptance test.

🤔

Two Red-Green-Refactor Loops








end


Failures:

1) Creating a blog post saves and displays the resulting blog post Failure/Error: click_on 'Create Blog Post'

AbstractController::ActionNotFound: The action 'create' could not be found for BlogPostsController

# app/controllers/blog_posts_controller.rb class BlogPostsController < ApplicationController def new ... end

def create end end


Failures:

1) Creating a blog post saves and displays the resulting blog post Failure/Error: click_on 'Create Blog Post'

ActionView::MissingTemplate: Missing template blog_posts/create

<%# app/views/blog_posts/create.html.erb %>


Failures:

1) Creating a blog post saves and displays the resulting blog post Failure/Error: expect(blog_post.title).to eq('Hello, World!')

NoMethodError: undefined method `title' for nil:NilClass



describe '#new' do ... end

describe '#create' do it 'creates a blog post record' do expect(BlogPost).to receive(:create).with(title: 'My Title', body: 'My Body') post :create, { blog_post: { title: 'My Title', body: 'My Body', } } end end end

# rspec spec/controllers/blog_posts_controller_spec.rb.F

Failures:

1) BlogPostsController#create creates a blog post record Failure/Error: expect(BlogPost).to receive(:create).with(title: 'My Title', body: 'My Body')

(BlogPost(id: integer, title: string, body: text) (class)).create({:title=>"My Title", :body=>"My Body"}) expected: 1 time with arguments: ({:title=>"My Title", :body=>"My Body"}) received: 0 times

# app/controllers/blog_posts_controller.rb class BlogPostsController < ApplicationController ...

def create BlogPost.create(params[:blog_post]) end end

☝😧 Wait for iiiiiiiit…

# rspec spec/controllers/blog_posts_controller_spec.rb..

Finished in 0.02774 seconds (files took 1.53 seconds to load)2 examples, 0 failures


Failures:

1) Creating a blog post saves and displays the resulting blog post Failure/Error: BlogPost.create(params[:blog_post])

ActiveModel::ForbiddenAttributesError


def create BlogPost.create(blog_post_params) end

private

def blog_post_params params.require(:blog_post).permit(:title, :body) end end


Failures:

1) Creating a blog post saves and displays the resulting blog post Failure/Error: expect(page).to have_content('Hello, World!') expected to find text "Hello, World!" in ""

<%# app/views/blog_posts/create.html.erb %> <h1><%= @blog_post.title %></h1>

<div> <%= @blog_post.body %> </div>


Failures:

1) Creating a blog post saves and displays the resulting blog post Failure/Error: <h1><%= @blog_post.title %></h1>

ActionView::Template::Error: undefined method `title' for nil:NilClass



...

describe '#create' do it 'creates a blog post record' do ... end

it 'returns the new blog post to the view' do blog_post = instance_double(BlogPost) allow(BlogPost).to receive(:create).and_return(blog_post) post :create, { blog_post: { title: 'My Title', body: 'My Body', } } expect(assigns[:blog_post]).to eq(blog_post) end end end

# rspec spec/controllers/blog_posts_controller_spec.rb..F

Failures:

1) BlogPostsController#create returns the new blog post to the view Failure/Error: expect(assigns[:blog_post]).to eq(blog_post)

expected: #<InstanceDouble(BlogPost) (anonymous)> got: nil

(compared using ==)


def create @blog_post = BlogPost.create(blog_post_params) end

... end

# rspec spec/controllers/blog_posts_controller_spec.rb...


# rspec....


# rspec spec/features/creating_a_blog_post_spec.rb.

Finished in 0.15204 seconds (files took 1.42 seconds to load)1 example, 0 failures



...

describe '#create' do it 'creates a blog post record' do expect(BlogPost).to receive(:create).with(title: 'My Title', body: 'My Body') post :create, { blog_post: { title: 'My Title', body: 'My Body', } } end

it 'returns the new blog post to the view' do blog_post = instance_double(BlogPost) allow(BlogPost).to receive(:create).and_return(blog_post) post :create, { blog_post: { title: 'My Title', body: 'My Body', } } expect(assigns[:blog_post]).to eq(blog_post) end end end



...

describe '#create' do let(:post_params) { { blog_post: { title: 'My Title', body: 'My Body', } } }

it 'creates a blog post record' do expect(BlogPost).to receive(:create).with(title: 'My Title', body: 'My Body') post :create, post_params end

it 'returns the new blog post to the view' do blog_post = instance_double(BlogPost) allow(BlogPost).to receive(:create).and_return(blog_post) post :create, post_params expect(assigns[:blog_post]).to eq(blog_post) end end end

# rspec....


Imagine if testing the way you want to was second-

nature.

TDD can help you get there.

…whether you end up embracing all of it or not.

🤔 Questions?

To Learn More

• learntdd.in/rails

• The RSpec Book

• Growing Object-Oriented Software, Guided By Tests

Thanks! 🙃@CodingItWrong learntdd.in/rails