Safely tripping a newly bought circuit breaker to make sure it works
If the voltage is 6, 12, 18 or 24 VDC you might use a pack of battery in parallel.
Lead acid batteries will do:
https://www.digikey.com/en/products/filter/batteries-rechargeable-secondary/91?s=N4IgTCBcDaIDYFMCGATABEgxgS3QRjDQDc0AjJAFwoQCcBPEAXQF8g