Validate Black Friday Discount Codes and Cart Rules With a Fixture Script

You are a careful ecommerce engineer who helps small shops catch promo bugs before Black Friday traffic hits. I want a small script that validates my discount codes and cart rules against a fixture cart before the sale goes live. Prefer a single file I can run locally. Do not invent my stack, promo engine, or storefront. Do not invent CLI flags or library APIs that may not exist; use well known approaches and tell me to confirm current options. If something is unclear, list it under [QUESTIONS] before the code.

Preferred language (Node.js or Python; pick one if I leave this blank and say which you chose): [STACK]
How I store promo rules today (JSON file, spreadsheet export, admin screenshots, paste of rules): [RULES SOURCE]
Sample discount codes and what each should do (percent off, fixed amount, free shipping, BOGO, stackable or not, min cart, excluded SKUs): [CODES]
A fixture cart as a list of line items with sku, name, unit price, quantity, and any tags like sale or excluded: [CART]
Currency and tax handling I care about (ignore tax, tax after discount, shipping separate): [MONEY RULES]
Where the script should print results (terminal table, JSON file, both): [OUTPUT]

Requirements:
1. Restate my rules in plain English and flag any conflicts (two codes both marked exclusive, a code that needs a min cart higher than my fixture, a BOGO with no clear eligible SKU).
2. Design a fixture format (JSON or simple Python/JS object) for cart lines and for each discount code. Keep it small and readable.
3. Write the validation script for [STACK]. For each code, apply it to the fixture cart according to the stated rules and report: eligible or not, discount amount, cart total after discount, and any reason it was rejected.
4. Include at least 3 automated assertions I can run as a tiny test: one code that should apply, one that should fail the min cart, and one that should refuse an excluded SKU. Use the language's built in assert or a minimal test runner; do not invent a heavy framework.
5. Handle edge cases honestly: empty cart, zero price items, quantity limits, rounding to 2 decimal places, and codes that claim to stack when my rules say they do not.
6. Add a short README section: how to install any dependency, how to edit the fixture, and how to run the script. Tell me to confirm library versions before I ship this into CI.
7. List [QUESTIONS] for anything I left blank that would change the math (tax inclusive prices, shipping discounts, gift cards).

Honest limits: this is a pre-sale fixture check, not a full checkout integration test. It will not replace testing the live cart on staging.

Deliverables:
1. Plain English rule restatement and conflict flags
2. Fixture format
3. Validation script
4. 3 assertions
5. README run steps
6. [QUESTIONS] list