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Testing in Rails: RSpec Tips and Tricks

Expert advice on how to write good RSpec tests

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Testing in Rails: RSpec Tips and Tricks
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Table of contents

What makes a good RSpec test?

RSpec is a testing framework written in Ruby to test Ruby code. To get started using RSpec with Rails, add it to the Gemfile.

group :development, :test do
  gem 'rspec-rails'

Next finish setting it up by running bundle install  in your project directory and then

rails generate rspec:install

It is easy to test for expected results, but how do you test for the unexpected? Good tests should include all edge cases, including best and worst-case scenarios; they should also be streamlined, very readable, and have redundancies eliminated.  


Readability is as much about containment as it is eliminating obfuscation, intentional or otherwise. 

Use contexts with scenarios to isolate possible edge cases. 

describe '#package_status' do
  context 'when package is delivered' do
    # it should send notice to customer
    # it should mark order as completed
  context 'when package is pending' do

  context 'when package is shipped' do
    # it should send notice to customer

Keep the waters from getting muddied when testing different methods; prepend `.` when testing class and `#` when testing instance. 

describe '#package_status' do

describe '.complete_orders' do

Ideally, you’ll keep each test as distinct and separate as possible so running down each one takes less work and makes for a more efficient process. 

Don’t Repeat Yourself: DRY up your tests

When you find yourself writing the same setup for multiple tests, put it in a shared context. Again, efficiency is the name of the game. Keeping tests as focused as possible will save time and effort. 

RSpec.shared_context 'pet_setup', shared_context: :metadata do
   let(:cat) { FactoryBot.create(:cat, name: ‘Mittens’, age: 10) }
   let(:dog) { FactoryBot.create(:dog, name: ‘Spot’, age: 2) }
   let(:fish) { FactoryBot.create(:fish, name: ‘Nemo’, age: 100) }

Shared examples are beneficial when testing the behavior of different types.

shared_examples 'pet_attributes' do |name, age|
  it 'returns its name' do
    expect(subject.name) to eq(name)
  it 'returns an age' do
    expect(subject.age) to eq(age)

describe '#pet_behavior' do
  include_context 'pet_setup'
  context 'when pet is a dog' do
    subject { dog }
    it_behaves_like 'pet_attributes', 'Spot', 2

  context 'when pet is a fish' do
    subject { fish }
    it_behaves_like 'pet_attributes', 'Nemo', 100

Speed up your Tests

Long test running times can be painful. If you’re keeping your tests separated and eliminating redundancies, you’ll want to zero in on any taking longer than they should. 

To see your top 10 slowest tests, append --profile to your rspec command.

bundle exec rspec spec/models/dog_spec.rb --profile

In controller tests, you can reduce network requests by using before blocks and modifying the parameters in each context.

describe '#post' do
  let(:user) { authorized_user }
  let(:order_params) { user_id: user.id, cart: shopping_cart }
  before do
    post 'orders' params: order_params
  context 'when user is authorized' do
      it 'returns a successful response'
      it 'returns a 200'
      it 'fires off a notification'
  context 'when user is not authorized' do
    let(:user) { unauthorized_user }
    It 'returns a flash message'
    It 'redirects user to a sign up page'

Resources to learn more about using RSpec with Ruby





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