Combine discounts: Check campaigns with a test matrix
A discount can work correctly on its own yet produce an unexpected result alongside another promotion. Before a campaign, test more than the advertised code. Check specific combinations with an automatic product discount, an order discount or a shipping offer. A small test matrix connects your intended rules with the checkout behaviour you actually observe.
Separate discount types before testing
Shopify distinguishes discounts on products, on the order subtotal and on shipping. Its official discount combination documentation states that each participating discount's settings must allow the relevant combination. Available combinations also depend on the requirements described there.
This calls for a targeted check in your own shop, rather than an assumption that every configuration will work. First record which promotions are active, how they are triggered and which products or orders they affect. A new campaign code may encounter an older automatic promotion that is easy to overlook during planning.
Write a short rule card
A fictional illustration shop is preparing a promotion for a selected group of posters. It records three rules for its test:
- A: A product discount should apply only to the selected poster group.
- B: An additional order code entered by the customer should not combine with A.
- C: A shipping promotion should combine with A when the specified conditions are met.
These are the intended rules for an example. The shop must check whether its available features can implement them precisely. Values, thresholds and active periods are filled in before testing; A, B and C are simply working labels.
For any threshold, record the amount to which you intend it to apply. “From €60” is an incomplete test specification until you have established which items count and whether the threshold is intended to be assessed before or after a discount.
Test eligible and excluded cases
A useful matrix includes more than the most favourable intended basket. It also shows what should happen outside the promotion:
| Test case | Expected result from the example rule card |
|---|---|
| One eligible poster with A active | A applies to that product |
| Only an ineligible item | A does not apply |
| An eligible poster plus another item | A changes only the eligible item |
| An eligible poster and code B | A and B do not apply together |
| An eligible poster meeting C's conditions | The intended combination of A and C is checked |
For the excluded pair A and B, also record which result the checkout actually chooses and which message appears. “Cannot be combined” does not automatically mean that your preferred code will win.
Compare the individual line item, subtotal and shipping line in every case. Shopify documents the sequence for combinable discounts as product, order and then shipping. Still verify the specific calculation in your configuration: different discount types cannot all be treated as arbitrary sequential percentages.
Check both sides of a threshold
If your promotion has a confirmed €60 threshold on a clearly defined calculation basis, prepare examples just below it, exactly at it and just above it. Values of €59, €60 and €61 are purely fictional test inputs here. They are not pricing or campaign recommendations.
Then change only one factor: remove an eligible item, alter a quantity or add the second code. This makes it easier to connect a discrepancy with a specific change. For time-limited rules, also check the start, end and timezone used by the system.
Run these checks in the safe test environment intended for your shop. Before completing anything, ensure that the process cannot trigger an unintended payment, production order or shipping release.
Separate observation from approval
For each test case, record the date, configuration, expected result and observed result. A screenshot can document the visible line items. Use clearly neutral test details in shared documentation, with no real personal information and no fictional customer identities presented as genuine.
What if a combination cannot work as planned? Adjust the rule card or configuration first, then test again. Do not simply change the advertisement while leaving the checkout behaviour unresolved.
Does a successful discount test demonstrate profitability? No. Cost calculations and technical rule testing are separate tasks. This exercise checks whether the advertised promotion matches the behaviour you observe.
Approve the campaign only when the excluded cases and threshold cases are also clearly documented. That gives you a reviewable decision rather than a single successful click.
AI-generated planning scene; a symbolic discount review, not a shop screenshot or an actual promotion or combination matrix.