Each experienced developer knows about Postman.
Postman is extensively used as a platform for running tests against API. But few know it could be used in the opposite way.
Postman provides really amazing feature - Mock Server. Indeed in modern software development, front-end and back-end teams are separated, and quite often - especially on new projects - has a huge discrepancy in the project plan. It means for some time back-enders have only the option to run end-to-end tests on API with Postman and front-enders should mock API inside their code to mock with some dummy endpoints.
Postman provides a better solution. You could create a collection of tests for API endpoints and create MockServer based on your collection. So once the front and back will be ready for integration they will be compatible and already tested.
I added a short gif to illustrate it.