API: cart maths, coupons and stock rules
App: SwagShop, a practice e-commerce demo store (Saucedemo-style). Login: standard_user, locked_out_user, problem_user, performance_glitch_user / secret_sauce. REST API: tests call it as /api/... through the request fixture or page.request; GET /api lists every endpoint ↗.
Interview scenario
"The cart service owns the money maths, so test it at the API: add two products with quantities, check the subtotal and 8% tax, apply SAVE10 and check the discount, prove an out-of-stock product is refused, then change a quantity and remove a line."
Acceptance criteria
- Log in through the API, then POST /api/cart/items for productId 4 with qty 2 and productId 0 (qty 1). Assert count 3 and subtotal 45.97.
- Apply coupon SAVE10 (POST /api/cart/coupon) and assert discount 4.6 and total 44.68 (tax is 8% after the discount).
- Adding productId 10 (out of stock) returns 409.
- PATCH /api/cart/items/4 with qty 1 and DELETE /api/cart/items/0, then assert the cart count is 1.
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