Effective Testing with RSpec 3

Refactoring

Both test cases have identical expressions setting up the ledger test double. You can remove the duplication by moving these into a common before hook. Place the following code just inside the first context block:

05-unit-specs/05/expense_tracker/spec/unit/app/api_spec.rb

let(:expense) { { 'some' => 'data' } }

before do
  allow(ledger).to receive(:record)
    .with(expense)
    .and_return(RecordResult.new(true, 417, nil))
end

Now, remove the setup code from both examples:

05-unit-specs/05/expense_tracker/spec/unit/app/api_spec.rb

it 'returns the expense id' do
  post '/expenses', JSON.generate(expense)

  parsed = JSON.parse(last_response.body)
  expect(parsed).to include('expense_id' => 417) ...