RSpec basics examples

examples.rb

# homework.rb

class Homework
  attr_reader :title, :content, :completed

  def initialize(title:, content:)
    @title = title
    @content = content
    @completed = false
  end

  def valid?
    return false if title.nil? || content.nil?

    true
  end

  def complete!
    @completed = true
  end
end

# student.rb

class Student
  attr_reader :name

  def initialize(name:)
    @name = name
  end

  def complete_homework(homework)
    homework.complete!
  end
end

# homework_spec.rb

require_relative '../../lib/homework.rb'

RSpec.describe Homework do
  subject { described_class.new(title: title,
                                content: content) }

  let(:title) { 'title' }
  let(:content) { 'content' }

  describe '#valid?' do
    context 'when title and content are present' do
      it 'is valid' do
        expect(subject.valid?).to eq true
      end
    end

    context 'when title is not present' do
      let(:title) { nil }

      it 'is not valid' do
        expect(subject.valid?).to eq false
      end
    end

    context 'when content is not present' do
      let(:content) { nil }

      it 'is not valid' do
        expect(subject.valid?).to eq false
      end
    end
  end

  describe '#complete!' do
    it 'sets completed state' do
      expect { subject.complete! }.to change { subject.completed }.from(false).to(true)
    end
  end
end

# student_spec.rb

require_relative '../../lib/student.rb'

# NOTE: ideally, you should have 70% unit tests and 30% integration tests

RSpec.describe Student do
  subject { described_class.new(name: name) }

  let(:name) { 'John Doe' }

  # unit-like example

  describe '#complete_homework' do
    let(:homework) { instance_double('Homework') }

    it 'sends complete! message to a homework' do
      expect(homework).to receive(:complete!).once

      subject.complete_homework(homework)
    end
  end

  # integration-like example

  describe '#complete_homework' do
    let(:homework) { Homework.new(title: '1', content: 'c')}

    it 'sends complete! message to a homework' do
      expect { subject.complete_homework(homework) }.to change { homework.completed }.from(false).to(true)
    end
  end

end