10.3. Unit testing and automated testing

Unit testing and automated testing are very important links in software development. They help to ensure the quality of the code and improve the reliability of the software. In this section, we will introduce the basic concepts and methods of unit testing, and how to use the JUnit framework for automated testing.

10.3.1. Unit testing

Unit testing is the process of testing the smallest testable component of a program, such as a method or a class. The purpose of unit testing is to ensure that each component performs its intended function correctly. Here are some basic principles for writing unit tests:

1. Test cases should be simple, self-contained and repeatable.
2. Test cases should cover various boundary conditions and abnormal situations of the program.
3. Test cases should be easy to understand and maintain.

10.3.2. JUnit framework

JUnit is a unit testing framework for Java programs, which provides a set of APIs for writing and running test cases. To use JUnit, you first need to add it to your project's dependencies. If you use Maven or Gradle, you can add JUnit dependencies in the corresponding configuration files.

The following is a simple example of writing unit tests using JUnit. Suppose we have a Calculatorclass that performs addition operations:

public class Calculator {
    public int add(int a, int b) {
        return a + b;
    }
}

To test the methods Calculatorof a class add, we can write a unit test like this:

import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.*;

public class CalculatorTest {
    @Test
    public void testAdd() {
        Calculator calculator = new Calculator();
        int result = calculator.add(1, 2);
        assertEquals(3, result);
    }
}

In this example, we use JUnit's @Testannotations to mark the test method, and use assertEqualsthe method to check whether the test results are as expected.

In addition assertEquals, JUnit also provides many other assertion methods, such as:

• assertTrue: Checks if a boolean is true.
• assertFalse: Checks if a boolean is false.
• assertNotNull: Checks if an object is not null.
• assertNull: Checks whether an object is a null.
• assertSame: Checks whether two objects are the same instance.
• assertNotSame: Check if two objects are not the same instance.

10.3.3. Automated testing

Automated testing refers to the process of using tools or scripts to automatically execute test cases. Automated testing can greatly improve the efficiency of testing and reduce errors in manual testing.

In Java projects, you can use build tools such as Maven or Gradle to implement automated testing. In these tools, all the test cases in the project can be automatically executed and a test report can be generated by simply running the corresponding test command.

For example, in a Maven project, you can run the following command to execute tests:

mvn test

In a Gradle project, you can run the following command to execute tests:

gradle test

To achieve automated testing, the following principles need to be followed:

1. Write test cases that are easy to understand and maintain.
2. Ensure that test cases are automatically executed in continuous integration and continuous deployment systems.
3. Fix test failures in a timely manner.

In short, unit testing and automated testing are the key to ensuring software quality. Mastering the use of testing frameworks such as JUnit and developing a good habit of writing test cases is very helpful for improving the quality and efficiency of software development. Recommended reading:

https://mp.weixin.qq.com/s/dV2JzXfgjDdCmWRmE0glDA

https://mp.weixin.qq.com/s/an83QZOWXHqll3SGPYTL5g