Test a Shopify subscription app contract before outsourcing changes

Follow one development-store contract through its first problem

Create a product with two variants and a selling plan whose interval is easy to recognize. Subscribe with a synthetic customer and test payment method. Connect the storefront choice, selling-plan group, subscription contract, first order, future billing schedule, and fulfillment by identifier. Checkout success is the start of the lifecycle, not proof that renewal and support paths agree.

Save the consent language shown before purchase. Compare price, interval, renewal terms, cancellation route, and inventory promise with the resulting contract. If copy and stored behavior differ, the merchant must decide which promise is authoritative before code changes data. A developer should not repair a contract by silently choosing whichever representation is easier to update.

Catalog edits do not automatically rewrite customer commitments

After the contract exists, change the catalog title and future product price. Remove one variant from sale without deleting the test record. Compare customer account, contract API, merchant interface, and next billing attempt. Record which details remain contractual and which reflect current catalog data. A subscription cannot be tested as a live pointer to a product page.

Change a selling plan separately from the contract. If the feature proposes a bulk contract change, require a preview with counts and examples. Test cancellation of the operation before any write. Existing customer agreements, price changes, and replacement variants require merchant policy. The implementation can show affected records and apply an approved action, but it must not invent consent.

Make failed billing and disordered events observable

Use the platform’s supported test mechanism for a failed billing attempt. Track attempt status, event delivery, merchant alert, customer message, retry schedule, and whether an order appears. The account page must not promise fulfillment for an unpaid attempt. Deliver a duplicate event and reorder related events in the handler fixture. Save the provider event identifier and make handling idempotent.

When arrival order is unreliable, fetch current contract truth before applying a destructive transition. Keep redacted event records only as long as policy allows. Trigger temporary API failure and revoked access. The app should surface an exception rather than making the contract look cancelled or healthy without evidence. Operators need a repair queue with last known state, attempted action, and allowed next steps.

Test account access, theme fallback, and uninstall

Open subscription controls through the supported customer account, then use a theme where the app block or JavaScript enhancement is unavailable. Check localized money and dates, keyboard focus, and failure messages. Customers need a truthful route to inspect the agreement even when a preferred drawer or block fails. A storefront screenshot does not cover contract management.

Uninstall and reinstall in the development store. Observe webhook subscriptions, stored tokens, theme remnants, contract visibility, and recovery. Uninstalling an app must not imply that customer contracts were cancelled. The handoff includes state diagrams, consent captures, API and event traces, billing failure, duplicate handling, account and fallback checks, uninstall behavior, and merchant decisions. Live contracts and communications remain merchant-controlled.

Follow one subscription through contract-changing events

Create test products and a customer whose names clearly mark them as fixtures. Start with the approved plan, then exercise upgrade, downgrade, quantity change, pause, resume, cancellation at period end, immediate cancellation if supported, and a payment failure. For each event, record the platform subscription identifier, application entitlement, effective time, billing period, proration result, webhook identifier, and visible customer state. Deliver the same webhook twice and deliver an older event after a newer one. The application should converge on the platform's authoritative contract without issuing duplicate credits, benefits, or notifications. Do not infer entitlement only from the last webhook received; fetch or reconcile authoritative state under a documented rule. Test the shop timezone against UTC near a billing boundary so a date label does not promise access for a day the platform considers expired. Copy exact money and interval values from the sandbox response rather than recreating them with floating-point arithmetic.

Separate commercial choices from integration mechanics. The owner must specify when a downgrade takes effect, what happens to excess usage, which failed-payment states retain access, and how cancellation language appears. The programmer should encode those decisions in a table-driven test, not invent them from provider status names. Revoke app access or rotate a test credential during reconciliation and ensure retries are bounded and visible. If an item or price becomes unavailable, the storefront should not silently substitute another plan. Inspect logs for tokens, customer fields, and webhook bodies; retain identifiers and categories needed for support while redacting private values. Run the full path with the app's production build against the dedicated test shop, then remove every test subscription and product. The handoff includes the event ledger, duplicate and out-of-order results, entitlement comparison, timezone cases, redacted failures, cleanup proof, and an explicit list of business rules awaiting approval. That package lets a reviewer distinguish a webhook transport bug from a disputed billing policy.

Verify storefront and administration views from the same event ledger. A shopper should not see a successful upgrade while the application still grants the old allowance, and support staff should be able to explain a pending change without reading webhook logs. Test browser refresh, two simultaneous change requests, and a back button resubmission against the sandbox. The second request must either join the first operation or fail with a clear current-state response. Reconcile after temporarily disabling webhook delivery, then restore delivery and prove historical events do not roll state backward. Measure how long a deliberately pending event remains before an alert. Capture provider API version and test-shop configuration because contract behavior can differ across revisions. Cleanup must confirm no fixture charge, entitlement, product, or customer remains available after the run.

Buyer questions

Questions about planning the role