/#-----------Null pointer exception when stubbing a method. check the syntax of your stub //# for me it was doReturn(responseEntity).when(rhpp.invokeDownStreamService(apiRequestService, traceId)); // this variable needs some other values to be set like url and good status ....use reflection api to set this field variables. Follow this link to understand partial Mocking. https://stackoverflow.com/questions/14970516/use-mockito-to-mock-some-methods-but-not-others Also understand difference between doReturn.when vs When.thenReturn. To directly answer your question, yes, you can mock some methods without mocking others. This is called a partial mock. See the Mockito documentation on partial mocks for more information. For your example, you can do something like the following, in your test: Stock stock = mock(Stock.class); when(stock.getPrice()).thenReturn(100.00); // Mock implementation when(stock.getQuantity()).thenReturn(200); // Mock implementation when(st...