Checkout calculates totals (pytest)

Generated output

### ✅ Checkout calculates totals

- **Given** the cart has 2 items
- **When** the user proceeds to checkout
- **Then** the subtotal should be $40.00
- **And** the tax should be $4.00
- **And** the total should be $44.00

pytest code

from executable_stories import story

def test_checkout_calculates_totals():
    story.init("Checkout calculates totals")
    story.given("the cart has 2 items")
    story.when("the user proceeds to checkout")
    story.then("the subtotal should be $40.00")
    story.then("the tax should be $4.00")
    story.then("the total should be $44.00")