RSpec basics

Recently I have re-studied the RSpec. This is just my reminder.

• describe
  • to be used to group something to be described. can be nested.
• context
  • same as describe but usually used to list some different conditions
• it
  • to be used to write test case. If it's a test for models or controller, it should have only one expectation.
• expect
  • to be used to describe an expectation. Several operators(to, not_to, etc) and matchers(be, eq, etc.) are available.
• subject
  • to be used to declare a test object which can be used implicitly after here - the following its sentence uses this to check the description method.

An easy example is below:

class Computer
  attr_accessor :cpu, :memory, :disk, :has_too_big_cpu

  def initialize(cpu, memory, disk)
    raise 'Non integer values given' unless
      cpu.is_a? Integer and memory.is_a? Integer and disk.is_a? Integer
    @cpu = cpu 
    @memory = memory
    @disk = disk

    @has_too_big_cpu = true if cpu > 10
  end 

  def description
    return "CPU: #{@cpu}, Memory: #{@memoory}, Disk: #{@disk}";
  end 
end

describe 'Computer' do
  describe 'initialization' do
    context 'with non-integer values' do
      it 'will raise an exception' do
        expect { Computer.new(1, 1, '10GB') }.to raise_error
          'Non integer values given'
      end 
    end 

    context 'with too big CPU' do
      it 'will set has_too_big_cpu' do
        computer = Computer.new(15, 1, 1)
        expect(computer.has_too_big_cpu).to be true
      end 
    end 
  end 

  subject { Computer.new(1, 1, 10) }

  its(:description) { should eq "CPU: 1, Memory: , Disk: 10" }
end