### Question:
PriceServiceImpl implements PriceService { @Override public PriceConfig findById(String id, HttpHeaders headers) { PriceServiceImpl.LOGGER.info("[Price Service][Find By Id] ID: {}", id); return priceConfigRepository.findById(UUID.fromString(id)); }  @Override Response createNewPriceConfig(PriceConfig createAndModifyPriceConfig, HttpHeaders headers); @Override PriceConfig findById(String id, HttpHeaders headers); @Override Response findByRouteIdAndTrainType(String routeId, String trainType, HttpHeaders headers); @Override Response findAllPriceConfig(HttpHeaders headers); @Override Response deletePriceConfig(PriceConfig c, HttpHeaders headers); @Override Response updatePriceConfig(PriceConfig c, HttpHeaders headers);  }### Answer:
@Test public void testFindById() { Mockito.when(priceConfigRepository.findById(Mockito.any(UUID.class))).thenReturn(null); PriceConfig result = priceServiceImpl.findById(UUID.randomUUID().toString(), headers); Assert.assertNull(result); }