Verify every critical path before going live. The most important items, in the order you should check them:
Checkout end-to-end: complete a full purchase with each supported payment method (card, digital wallet, COD if applicable) and verify the order appears in admin with correct details. Verify the order confirmation email is sent and contains correct information. Verify the inventory decrement happens correctly.
Email notifications: test every automated email (order confirmation, shipping notification, abandoned cart, password reset) for content accuracy, correct branding, and correct links. These are often the last thing tested and the first thing customers see.
Analytics and tracking: verify Google Analytics, Google Tag Manager, Facebook Pixel, and any other tracking pixels are firing correctly on all page types. Verify conversion events are recording. This is the step most frequently forgotten — and losing 3 weeks of post-launch analytics data is a significant cost.
Search and filtering: verify that your collection pages and search results return correct products, that filtering works correctly, and that sort orders match your merchandising intent.
Mobile checkout: verify the full checkout flow on a real mobile device, not just a browser's mobile emulation. Real device testing catches rendering and interaction issues that emulation misses.