Mockito - @Spy vs @Mock

java unit-testing mocking mockito spy
Abhinav picture Abhinav · Feb 3, 2015 · Viewed 85.9k times · Source

Mockito - I understand a spy calls the real methods on an object, while a mock calls methods on the double object. Also spies are to be avoided unless there is a code smell. However, how do spies work and when should i actually use them? How are they different from mocks?

Answer

Crazyjavahacking picture Crazyjavahacking · Feb 3, 2015

Technically speaking both "mocks" and "spies" are a special kind of "test doubles".

Mockito is unfortunately making the distinction weird.

A mock in mockito is a normal mock in other mocking frameworks (allows you to stub invocations; that is, return specific values out of method calls).

A spy in mockito is a partial mock in other mocking frameworks (part of the object will be mocked and part will use real method invocations).

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