The Chipmunk has 2 fuel pumps, both mechanical diaphragm types, in parallel. Both feed the carburetor simultaneously and one is used to prime the engine as well, using a manual lever.
If the one used for priming fails you'd know because you'd not be able to prime the engine. But if the other one failed you wouldn't know you were relying on just one until the first failed as well (at some point after priming), when the engine would stop!