gb|rspec example

class CPU
  attr_reader :f

  def initialize
    @f = 0x00
  end

  def instruction
    if @f & 0x10 == 0x10
      # do something
    else
      # do something else
    end
  end
end

### RSPEC
describe CPU
  let(:cpu) { CPU.new }
  describe '#instruction' do
    context 'when register state is 0x10' do
      before { CPU.instance_variable_set "@#{f}", 0x10 } # <-- can this be improved?
      it 'does something'
    end

    it 'does something else'
  end
end