Java development: How to do code coverage testing and reporting

Java Development: How to Conduct Code Coverage Testing and Reporting

In Java development, code coverage testing is an important tool that can help us identify tests Do the use cases cover various parts of the code and understand the testing quality of the code. This article describes how to conduct code coverage testing and generate corresponding reports, and provides some specific code examples.

Code coverage testing measures the coverage of each part of the code by running test cases and collecting execution information. In Java development, commonly used code coverage testing tools include JaCoCo and Emma. This article will use JaCoCo as an example to explain.

Step 1: Add the JaCoCo plug-in

First, add the JaCoCo plug-in to your Java project. You can use build tools such as Maven or Gradle to add relevant dependencies and configurations to the project's pom.xml or build.gradle file.

For Maven projects, you can add the following dependencies in the pom.xml file:

<build>
    <plugins>
        <plugin>
            <groupId>org.jacoco</groupId>
            <artifactId>jacoco-maven-plugin</artifactId>
            <version>0.8.5</version>
            <executions>
                <execution>
                    <id>jacoco-initialize</id>
                    <phase>initialize</phase>
                    <goals>
                        <goal>prepare-agent</goal>
                    </goals>
                </execution>
                <execution>
                    <id>jacoco-report</id>
                    <phase>test</phase>
                    <goals>
                        <goal>report</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

For Gradle projects, you can add the following configurations in the build.gradle file:

plugins {
    id 'jacoco'
}

jacoco {
    toolVersion = '0.8.5'
}

test {
    finalizedBy jacocoTestReport
}

jacocoTestReport {
    reports {
        xml.enabled = true
        html.enabled = true
    }
}

The above configuration will start JaCoCo's agent and generate a coverage test report after the test is completed.

Step 2: Run the test case

After writing the test case in the project, use the build tool to execute the test command, for example, use Maven to execute the mvn test command, or use Gradle executes the ./gradlew test command. After the test is completed, JaCoCo will generate a coverage test report.

Step 3: Generate coverage test report

After executing the test command, you can find the generated coverage test report in the project directory. For Maven projects, reports are generated in the target/site/jacoco/ directory by default; for Gradle projects, reports are generated in the build/reports/jacoco/ directory by default.

In the generated report, you can view the code coverage. There are usually indicators such as row coverage, branch coverage, and class coverage.

Next, let’s look at specific code examples.

Suppose we have a class named Calculator, which has an add method for adding two numbers:

public class Calculator {
    public int add(int a, int b) {
        if (a > b) {
            return a + b;
        } else {
            return b - a;
        }
    }
}

Let’s write test cases and conduct code coverage testing.

import static org.junit.Assert.assertEquals;
import org.junit.Test;

public class CalculatorTest {
    @Test
    public void testAdd() {
        Calculator calculator = new Calculator();
        int result = calculator.add(3, 5);
        assertEquals(8, result);
    }
}

After executing the test command, JaCoCo will generate a coverage test report. Opening the report, we can see that in the Calculator class, the line coverage of the add method is 100%, and the branch coverage is also 100%.

Through code coverage testing and reporting, we can find out whether test cases cover various branches and situations of the code, helping us improve the quality and reliability of the code.

To sum up, this article introduces how to conduct Java code coverage testing and generate corresponding reports. Through the use of JaCoCo tools, we can better understand and improve the quality of test code. At the same time, specific code examples are provided to illustrate how to apply code coverage testing in actual projects.

Hope this article is helpful to you!

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