Hey there @SW,
Thanks for joining us here in the community! We are thrilled to have you with us 🙂
You can absolutely create a test label in ShipStation! My recommendation to do so would be to create a mock-up testing order directly in the integration, just as you said, to test that connection. Once that test order is imported into the system, utilize a "post ship" billed carrier directly like UPS or FedEx that only charges for labels once they have been scanned in by the carrier directly. This will prevent you from purchasing a label that will not be used to actually send a shipment.
Additionally, you can test out the physical printing of the formatting for your labels from the Printer settings. Starting at Settings (gear icon in the top right) > Printing > Printing Setup > Document Options next to labels > adjust your formatting accordingly > Preview > Print.
I hope this helps!
If you utilize a stand alone UPS or FedEx account - one that is NOT connected to the ShipStation wallet - you should not have to add money to an account to create those test tables. Any carrier that is post-billed, would not charge for labels until they are scanned in so you can continue to create them in tests without actually purchasing a label.
I hope this helps! 🙂