Test discount code application at checkout

Failure modes in this flow

Discount bugs cluster in a small number of places, and each one needs a different assertion to catch it.

• An invalid code is accepted - the field takes anything and the total silently changes, or the error never appears.
• The badge and the maths disagree - the page confirms "10% off applied" while the line item deducts a different amount.
• The discount does not reach the total - the line item renders correctly but the total is unchanged.

Testing the unhappy path first is the part most teams skip. This test types NOTACODE before it types WELCOME10, so a field that accepts anything fails at step two rather than passing the whole run.

Writing the objective

The objective is written so each assertion is a string the shopper can see. The error message is quoted in full, including the code name, because a generic error is a different bug from a correctly targeted one.

---
mode: testing
url: https://my-testing-repo-main.vercel.app/shopify-clone-app?reset=true
max_steps: 45
tags: [shopify, e-commerce, discount]
---

# Shoplify 2.2: Discount code application

Catalog objective: apply a discount code at checkout and verify the reduced total.
Key assertion: discount line item matches the expected percent.

## Add a product and open checkout
Click "Add to cart" on "Heavyweight Cotton Tee", click "View cart", click "Checkout", and verify the order summary shows a Total of "$41.06".

## Apply an invalid code first
Type "NOTACODE" into the "Discount code" field, click "Apply", and verify an error appears reading "Discount code NOTACODE isn't valid for this order."

## Apply the ten percent code
Clear the discount field, type "WELCOME10", click "Apply", and verify a badge appears reading "WELCOME10 (10% off) applied".

## Confirm the discounted total
Verify the summary shows a discount line "Discount (WELCOME10)" of "−$3.20" and a Total of "$37.60".

Step four is the arithmetic check. It asserts the discount line reads 3.20 off and the total lands at $37.60, which is what ten percent of the $32.00 subtotal should produce against a $41.06 pre-discount total. Run it with:

kane-cli testmd run tests/shopify/discount-code_test.md

Running it locally

Four steps, four passes. The first step is the slowest at 60.1 seconds because it chains three navigations, add to cart through to the checkout page, before its assertion.

---
test: ../discount-code_test.md
status: passed
started: 2026-09-15T09:21:50.747Z
duration_s: 174
session_id: 2d3b01a6-5014-4bf3-9c3e-75d277a7f921
---

# Shoplify 2.2: Discount code application - Result

## Add a product and open checkout ✓ passed (60.1s)
md5: e78d860c73d44fa658232026c1a1bde1
Click "Add to cart" on "Heavyweight Cotton Tee", click "View cart", click "Checkout", and verify the order summary shows a Total of "$41.06".

## Apply an invalid code first ✓ passed (33.1s)
md5: 5eb4fb64e9a382ff46fe43df8f7cf2da
Type "NOTACODE" into the "Discount code" field, click "Apply", and verify an error appears reading "Discount code NOTACODE isn't valid for this order."

## Apply the ten percent code ✓ passed (40.9s)
md5: a0c09a7e6123d93a3b59d033832a9860
Clear the discount field, type "WELCOME10", click "Apply", and verify a badge appears reading "WELCOME10 (10% off) applied".

## Confirm the discounted total ✓ passed (35.9s)
md5: cdd2b6341ec07546d92ac66b7fd1ae52
Verify the summary shows a discount line "Discount (WELCOME10)" of "−$3.20" and a Total of "$37.60".

Putting it in CI

The result is a promo regression test that can be cloned per campaign by changing two strings. Each campaign gets its own file, and the suite grows without any new code.

For a campaign calendar with several codes live at once, generating the variants beats writing them. Test case generation with Kane CLI covers drafting a family of flows from one description, and live page assertions explains how each check is verified before it is recorded.