TDD in the real life

Initial scenario:

• read products from DB
• retrieve price from external service

Problems:

• no tests
• mixin of data access and business logic
• random prices
• OOP?

Desired features:

• pay with external service and if payment succeeded empty cart
• if payment succeeded save bill results on S3 bucket bills
• if cart has more than three items send big_cart_created message on SQS events_queue