Separate test and live API keys — passes issued in test mode carry a visible [TEST] watermark and never touch your production numbers.
You should be able to break things while you integrate. API keys now come in two modes:
[TEST] watermark on the pass faceWire up your integration against a test key, install the watermarked passes on your own phone, and flip to live when it works. Create both kinds under Developers → Keys.
Free for 10 active passes. No card required.