How does Mockito's reset method interact with @Spy annotations in terms of method calls

Mockito's `reset` Method

The `reset` method in Mockito is used to reset mock objects. This means it clears all stubbing and invocations recorded on the mock, allowing it to be reused in a test class. However, using `reset` is generally discouraged because it can lead to complex and poorly designed tests. Instead of resetting mocks, it's often better to create new mocks when needed[1][4][7].

Mockito's `@Spy` Annotation

The `@Spy` annotation in Mockito is used to create a spy object, which is a real object with some methods mocked. This allows for partial mocking, where some methods retain their original behavior while others are mocked. Spies are particularly useful when you want to test a class with some real method calls and some mocked method calls[5][6].

Interaction Between `reset` and `@Spy`

When using `@Spy`, you are working with a real object that has some methods potentially mocked. If you use `reset` on a spy, it will reset any stubbing you have done on the spy, but it will not affect the real object's behavior. However, since spies are real objects, resetting them does not change their underlying behavior; it only clears any stubbing or invocation counts related to the spy.

For example, if you have a spy on an object and you've stubbed one of its methods using `doReturn`, calling `reset` on the spy will remove this stubbing. After resetting, calling the stubbed method will execute the original method unless you reapply the stubbing.

java
// Example usage
MyClass spy = spy(new MyClass());
doReturn("Mocked").when(spy).myMethod();
// Resetting the spy removes the stubbing
reset(spy);
// Now, calling myMethod() will execute the original method

In summary, `reset` affects the mock-related state (stubbing and invocation counts) of a spy but does not alter the behavior of the underlying real object. It's essential to be cautious when using `reset` with spies to avoid unintended behavior in your tests.

Best Practices

- Avoid Using `reset`: It's generally recommended to avoid using `reset` and instead create new mocks or spies when needed to keep tests simple and clear.
- Use `@Spy` Wisely: Use `@Spy` when you need to partially mock an object, ensuring that you understand how it interacts with the real object's behavior.
- Stubbing with Spies: Always use `doReturn`, `doThrow`, etc., when stubbing methods on spies to avoid calling the original methods unintentionally[2][6].