• A stub interface simulates an actual object by having a small number of methods. It's a type of object that has pre-existing data and always returns the same value regardless of the input. Furthermore, we mostly employ it when we don't want the real object to respond.
• The mock is an interface that we programme to compare the outputs from the tests to the expected outcomes. We frequently use third-party libraries such as Mockito and JMock to accomplish this. It's particularly useful when we're working with a large test suite and each test demands a different set of data.
• Stubs offer input for the application under test, allowing the test to be run on something other than the application under test.
• Mocks provide information to the test that helps it determine whether it should pass or fail.
• A stub is for the application, while a mock is for the test

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