Cash Register

Not cheap and fast What if printer is broken, the CashRegister will fail in production Spy? verify(mockPrinter).printer(”purchased item”);

Mock is a fake object which has the same contract as the dependency Mock Printer is spying on the dependency for testing Cash Register → Purchase → Item Cash Register (transitive dependency) Item items.stream().map(Objects::toString).collect(Collectors.joining(”, ”)); when(stubbedPurchase.asString()).thenReturn(”stubbed items”) → overriding of the method mock → used to assert the behaviour of the dependency stub → used to return dummy values for testing mock api, database, server, network call Mock will spy method call, arguments and how many times the method has been called Mock won’t spy on the private methods, because it only fakes the contract which is exposed Hierarchy or tools to know what is dependant on what We cannot mock constants