context_driven_rspec.rb

include_context 'api session'
let(:path) { "/api/v1/#{order_id}/line" }
let(:order_id) { 456 }

context 'when do some complex things' do
  let(:order) { FactoryBot.create(:order) }
  let(:order_id) { order.id }
  let(:item) { LineItem.last }
  let(:valid_params) do
    {
      name: 'product 1',
      price: 1.14
    }
  end
  let(:valid_response) do
    {
      id: order_id,
      items: [
        {
          name: item.name,
          price: item.price.to_s
        }
      ]
    }
  end

  it 'does something special' do
    allow(ExternalService).to receive(:get_info)
    expect(ExternalService).to receive(:get_info)
    
    expect { do_post }.to change { LineItem.count }.by(1)
    
    assert_200_json_response_object
    expect(order.reload.line_items).to eq [item]
  end
end