Introduction to Test-Driven Development (TDD) with RSpec

What is TDD?

Test-Driven Development (TDD) is a software development methodology that inverts the traditional programming process. Instead of writing code and then testing it, TDD proposes writing tests first.

The Red-Green-Refactor Cycle

TDD follows a simple but powerful cycle:

1. Red: Write a failing test
2. Green: Write minimal code to make the test pass
3. Refactor: Improve the code while keeping tests green

Setting up RSpec in Rails

To get started with TDD in Rails, we need to configure RSpec:

# Gemfile
group :development, :test do
  gem 'rspec-rails'
  gem 'factory_bot_rails'
  gem 'shoulda-matchers'
end

Practical Example

Let's see an example of how to implement TDD for a User model:

# spec/models/user_spec.rb
RSpec.describe User, type: :model do
  describe 'validations' do
    it 'requires an email' do
      user = User.new(email: nil)
      expect(user).not_to be_valid
      expect(user.errors[:email]).to include("can't be blank")
    end
  end
end

"TDD is not about testing, it's about design. Tests are just a beneficial side effect."

Benefits of TDD

• Better code design
• Greater confidence in changes
• Living documentation of behavior
• Fewer bugs in production