Create unit tests
Unit tests should be created for proffesionalism (and to make future changes break less) Additionally, test scripts could be written to test out the API directly (python/bash scripts, postman scripts, etc. pick one :D)
An example of postman tests: https://learning.postman.com/docs/tests-and-scripts/write-scripts/test-examples/
Edited by Abonyi Bence Péter