Use the Mockito framework to perform the simulation test of the Java class library

Use the Mockito framework to perform the simulation test of the Java class library Summary: Mockito is a popular Java framework that uses the simulation operation of the Java library during unit testing.This article will introduce the basic concepts and usage methods of the Mockito framework, and provide some Java code examples to illustrate how to use Mockito for simulation testing. Introduction: In software development, unit testing is a very important activity.However, in some cases, we cannot directly test the JAVA library that depends on the JAVA library, which may be due to external dependence and the restrictions on the test environment.At this time, we can use the Mockito framework to simulate the behavior of these class libraries to ensure that our code can interact correctly with them. 1. Introduction to Mockito Mockito is an open source Java framework for simulation testing.It provides simple and easy -to -use APIs to help us easily create and manage simulation objects.Using Mockito, we can simulate various types of Java libraries, including interfaces, abstract classes and specific classes. The Mockito framework can help us complete the following tasks: 1. Simulation object: Mockito can create analog objects and define their behavior. 2. Verification behavior: Mockito can verify the interactive behavior of analog objects, such as the number of calls, parameters, etc. of the method. 3. Set the expected value: Mockito can set the expected value of an analog object to check whether they meet the expectations in the test. 2. How to use Mockito 1. Import dependencies First, we need to import the dependencies of the Mockito framework in the project.The following dependencies can be added to the Maven or Gradle project: <dependency> <groupId>org.mockito</groupId> <artifactId>mockito-core</artifactId> <version>3.12.4</version> <scope>test</scope> </dependency> 2. Create analog object It is very simple to use the Mockito framework to create analog object.The following is an example of creating analog object: import org.mockito.Mockito; // Create an analog object of an interface List<String> mockedList = Mockito.mock(List.class); // Create a concrete simulation object ArrayList<Integer> mockedArrayList = Mockito.mock(ArrayList.class); 3. Define the behavior of the simulation object Defining behavior in analog objects is very important.We can use Mockito's WHEN-THEN structure to set the behavior of analog objects.The following is an example of setting an analog object behavior: import org.mockito.Mockito; List<String> mockedList = Mockito.mock(List.class); // When defining when mockedList.get (0) is called, the "Mockito" string is returned Mockito.when(mockedList.get(0)).thenReturn("Mockito"); // When defining when mockedList.size () is defined, return 1 Mockito.when(mockedList.size()).thenReturn(1); 4. Verify the behavior of the simulation object Using Mockito can verify whether the behavior of the analog object meets the expectations.The following is an example of verifying the behavior of analog object: import org.mockito.Mockito; List<String> mockedList = Mockito.mock(List.class); // The method of calling an analog object mockedList.add("Test"); // Verify whether the ADD method has been called once, and the parameter is "test" Mockito.verify(mockedList).add("Test"); 5. Set the expected value of the analog object Sometimes, we need to set the expected value of an analog object and check in the test.The following is an example of setting an analog objective value and checking: import org.mockito.Mockito; List<String> mockedList = Mockito.mock(List.class); // Set the expected value of the analog object as empty Mockito.when(mockedList.get(0)).thenReturn(null); // Test whether the expected value in the test code is empty assertNull(mockedList.get(0)); 3. Summary The Mockito framework is a powerful and easy -to -use Java unit test framework, which is very useful when simulating the Java class library.In this article, we introduce the basic concepts and usage methods of Mockito, and provide some Java code examples to illustrate how to use Mockito for simulation tests.By using Mockito, we can better test our code and maintain the maintenance and reliability of the code.