Mockito

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Mockito is a popular open-source Java framework used for creating mock objects in unit testing. Mock objects are simulated objects that can be used to replace real objects during testing. This allows you to isolate the code under test and focus on its behavior without being affected by the behavior of the real objects. Mockito allows you to simulate the behavior of dependencies or external systems that your code interacts with during testing. With Mockito, you can create mock objects, define their behavior, and validate the interactions with those objects.

Mockito provides a simple and intuitive API for creating mock objects, stubbing methods, and validating method invocations. It helps you write more reliable and maintainable unit tests.

Examples of Mockito

• In your banking application, you can use Mockito to create a mock object for the database layer and simulate different responses (e.g. successful transactions, errors, and timeouts) to test your unit.
  
• You can use Mockito to mock external payment gateway APIs in your e-commerce system. This allows you to test the order processing logic of your unit with different payment response types (e.g. successful payments, declined payments, and timeouts).
• In your healthcare application, you use Mockito to mock a patient data repository. This enables you to test different patient data retrieval scenarios.
• You use Mockito to create mock objects for user authentication services in your social media platform. It helps you simulate different authentication scenarios (e.g. successful logins, invalid credentials, and account lockouts).
• In your logistics system, you use Mockito to mock GPS tracking services. This allows you to test location-based features and simulate different GPS responses (e.g. accurate coordinates, no signal, and unexpected errors).

Tips for Mockito

• Focus on testing the behavior of the code rather than its internal implementation details when using Mockito.
• Use Mockito annotations, such as annotations below, to simplify the creation and injection of mock objects.

  @Mock

  @InjectMocks

• Ensure test coverage by verifying the interactions with mock objects using Mockito's verification methods, such as

  verify

• Avoid excessive mocking and prefer using real objects whenever possible to maintain the integrity of your tests.

FAQ (interview questions and answers)

1. Can Mockito be used with other testing frameworks?
   Yes, Mockito can be used with various testing frameworks in the Java ecosystem, such as JUnit and TestNG.
2. Can Mockito mock static methods or final classes?
   No, Mockito cannot mock static methods or final classes. It is designed to mock interfaces, abstract classes, and concrete classes.
3. Is Mockito suitable for integration testing?
   No, Mockito is intended for unit testing and mocking dependencies.
4. Can Mockito be used in Android application testing?
   Yes, Mockito can be used in Android application testing if Java programming language is being used in Android development.

Remember to just comment if you have any doubts or queries.

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