Mockito Tutorial: Learn mocking with 25 Junit Examples - Step 13: Mockito Spy

The video tutorial explains the concept of spies in Mockito, how to create and use them, and their differences from mocks. It covers creating a mock, understanding the functionality of spies, and using spies to track method calls. The tutorial also discusses when to use spies versus mocks, emphasizing that spies are more suitable for legacy systems where code access is limited.

What is the primary purpose of using a spy in Mockito?

• To completely replace the functionality of a class

• To simplify the code structure

• To track method calls while retaining original functionality

• To enhance the performance of a test

What is the default behavior of a mock in Mockito?

• It performs the actual method logic

• It logs the method call

• It returns a default value

• It throws an exception

How can you change the return value of a method in a mock?

• By using the 'modify' method

• By using the 'replace' method

• By using the 'stub' method

• By using the 'override' keyword

What is a key difference between a mock and a spy?

• A spy replaces all methods, a mock does not

• A spy can track method calls, a mock cannot

• A mock can track method calls, a spy cannot

• A mock retains original functionality, a spy does not

In what scenario is it more appropriate to use a spy instead of a mock?

• When you need to test a new feature

• When you want to track method calls in a legacy system

• When you want to improve test performance

• When you need to simplify the code

What happens when you add an element to a spy of an ArrayList?

• An exception is thrown

• The size of the list increases

• The size of the list remains unchanged

• The list is cleared

How can you verify that a method was never called on a spy?

• By using the 'check' method

• By using the 'verify' method with 'never'

• By using the 'assertNever' method

• By using the 'confirm' method

Why might spies be considered complex to maintain?

• They do not support method verification

• They require more code

• They are slower than mocks

• They mix real and stubbed functionality

What is a potential downside of using spies in a project?

• They cannot be used with legacy systems

• They make the code less readable

• They can lead to confusing test results

• They do not support stubbing

In most scenarios, what is the preferred choice between mocks and spies?

• Mocks, because they are simpler to use

• Mocks, because they are faster

• Spies, because they are more flexible

• Spies, because they are more powerful