Code Coverage and Reporting - Maven Tutorial

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Code coverage is a metric used in software development to measure the degree to which the source code of a program is executed during automated tests. It provides insights into the effectiveness of the tests and helps identify areas of the code that may require additional testing. Apache Maven offers tools and plugins that make it easy to measure and generate code coverage reports. In this tutorial, we will explore code coverage and reporting using Apache Maven.

Introduction to Code Coverage and Reporting

Code coverage is a measure of how much of your source code is being executed by your tests. It helps you determine the areas of your codebase that have been tested and identify potential gaps in your test suite. Code coverage reports provide detailed information about the lines, branches, and methods that have been covered or missed during the test execution.

Steps to Measure Code Coverage and Generate Reports with Maven

Measuring code coverage and generating reports using Maven involves the following steps:

  1. Adding a code coverage plugin to the build configuration
  2. Configuring the code coverage plugin
  3. Running the tests and generating the code coverage report

Adding a Code Coverage Plugin

To measure code coverage with Maven, you need to add a code coverage plugin to your project's build configuration. The most commonly used plugin for code coverage in Maven is the JaCoCo (Java Code Coverage) plugin. Add the following plugin configuration to the <build> section of your project's POM file:






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This configuration adds the JaCoCo plugin to your project and configures it to generate code coverage reports during the prepare-package phase.

Configuring the Code Coverage Plugin

The code coverage plugin needs to be configured to include the desired classes and generate the appropriate report formats. You can customize the configuration by adding the following code within the <configuration> element of the JaCoCo plugin configuration:




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This configuration specifies that code coverage should only be measured for classes in the com.example.myapp package and generates both HTML and XML report formats. Adjust the package pattern according to your project's package structure.

Running Tests and Generating the Code Coverage Report

To run the tests and generate the code coverage report, use the following command in the terminal or command prompt within your project's directory:

mvn clean test

Maven will execute the tests and generate the code coverage report based on the configuration provided. The generated report will be available in the target/site/jacoco/ directory of your project.

Common Mistakes to Avoid

  • Not adding the code coverage plugin to the project's build configuration
  • Excluding important classes or packages from code coverage analysis
  • Forgetting to run the tests before generating the code coverage report
  • Not regularly reviewing and analyzing the code coverage reports

Frequently Asked Questions

  1. What is a good code coverage percentage?

    There is no definitive answer to this question as the desired code coverage percentage may vary depending on the project and its specific requirements. However, a commonly recommended threshold is to aim for at least 80% code coverage.

  2. Can I exclude specific classes or methods from code coverage analysis?

    Yes, you can exclude specific classes or methods from code coverage analysis by configuring the JaCoCo plugin in your project's POM file. Use the <excludes> or <exclude> element within the plugin configuration to specify the classes or methods to be excluded.

  3. How often should I generate code coverage reports?

    It is recommended to generate code coverage reports regularly, ideally after every test execution or as part of your continuous integration process. This helps track the progress of your tests and identify any gaps in code coverage.

  4. Can I generate code coverage reports in different formats?

    Yes, the JaCoCo plugin supports generating code coverage reports in various formats, including HTML, XML, CSV, and more. You can configure the <reportFormats> element within the plugin configuration to specify the desired report formats.

  5. Can I integrate code coverage reports with other tools or services?

    Yes, code coverage reports can be integrated with other tools or services for further analysis. For example, you can integrate code coverage reports with SonarQube, a popular code quality and analysis platform, to get a comprehensive view of your project's test coverage.


Code coverage and reporting play a vital role in assessing the effectiveness of tests and identifying areas of improvement in your software projects. With Apache Maven and the JaCoCo plugin, you can easily measure code coverage and generate detailed reports. By following the steps outlined in this tutorial, you can configure the code coverage plugin, run tests, and generate code coverage reports. Regularly reviewing and analyzing the reports will help you ensure sufficient test coverage and improve the overall quality of your software.