Best Code Coverage Tools for Java and Node

What are Code Coverage Tools?

Code coverage tools merge and integrate with testing software to provide developers with a measure of tested code. They essentially show you how much of your code actually ran during the test. Additionally, they can seamlessly integrate with DevOps code quality tools to provide more detailed results.

As you run your tests, these tools analyze and calculate the code executed. Plus, if you run different tests, they can churn out separate reports for each in one file. A good tool will provide you with a report of various testing such as unit, integration, functional, end-to-end, etc.

In this article, we'll present our top choices for Java and Node.js code coverage that we recommend you explore. Here are our selected options.

1. JaCoCo (Java Code Coverage)

JaCoCo stands for Java Code Coverage. It is an open-source code coverage library and free tool based on Java bytecode. JaCoCo provides information about code coverage in various formats, such as HTML, XML, CSV, and JaCoCo execution data files (*.exec).

In addition, it offers customizable color coding to highlight fully, partially, and uncovered lines. This feature applies to your own source code as well as sources linked to instrumented external libraries. Furthermore, JaCoCo supports various JVM languages and is compatible with all released Java class file versions.

The tool tracks each instruction, showing which lines or branches were executed and which were missed during testing. Clicking on the report allows you to identify uncovered and partially covered portions, among other details.

Features: 

• It can be easily integrated into Java applications using a Java agent and can instrument code.
• It provides an API for custom integration scenarios. 
• It provides a remote protocol and JMX(Java Management Extensions) control, enabling users to request execution data dumps from the coverage agent remotely and at any desired moment.
• It includes Ant tasks for automation tasks to collect and manage execution data. 
• It provides a Maven plugin to gather data about how much of their code is tested. 
• We can import the Jacoco report into other code quality tools like SonarQube and Jenkins.
• You can integrate it with popular build systems, testing tools, IDEs, frameworks, and Java VM-based applications such as Spring Boot, JUnit, Maven, Gradle, and Eclipse, plain Java programs, OSGi frameworks, web containers, or EJB servers.

Installation

To use JaCoCo, you typically add it as a plugin to your build tool. For example, in a Maven project, you can include it in your pom.xml:

<build>
    <plugins>
        <plugin>
            <groupId>org.jacoco</groupId>
            <artifactId>jacoco-maven-plugin</artifactId>
            <version>0.8.7</version>
            <executions>
                <execution>
                    <goals>
                        <goal>prepare-agent</goal>
                    </goals>
                </execution>
                <execution>
                    <id>report</id>
                    <phase>test</phase>
                    <goals>
                        <goal>report</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

Alternatively, it can be used with Gradle:

apply plugin: "jacoco"
jacocoTestReport {
reports {
cxml.enabled true
csv.enabled true
html.enabled true
}
}
test {
finalizedBy jacocoTestReport
testLogging {
events "passed", "skipped", "failed"
afterSuite { desc, result ->
if (!desc.parent) { // will match the outermost suite
println "Results: ${result.resultType} (${result.testCount} tests, ${result.successfulTestCount} successes, ${result.failedTestCount} failures, ${result.skippedTestCount} skipped)"
}
}
}
}

You can then run your tests as usual, and JaCoCo will generate a coverage report in the target/site/jacoco directory.

2. Cypress (Node.js, JavaScript, TypeScript)

Cypress is a popular end-to-end testing framework for web applications that also includes built-in support for code coverage. It can be leveraged to generate code coverage reports for Node.js, JavaScript, and TypeScript applications.

Features:

• Integrated code coverage support for web applications.
• End-to-end testing capabilities for web applications with real browser interactions.
• Automatic instrumentation of your code for coverage analysis.
• Generation of code coverage reports, including coverage statistics for each file.
• Support for running tests in headless mode for continuous integration.
• Ability to easily incorporate code coverage into your existing testing workflow.

Installation

To set up Cypress code coverage, you need to install the @cypress/code-coverage package and configure Cypress to use it. Here's how you can do it:

npm install --save-dev @cypress/code-coverage

Next, in your Cypress configuration file (e.g., cypress.json), add the following:

{
  "pluginsFile": "path/to/your/plugins/index.js"
}

In your plugins file (e.g., cypress/plugins/index.js), include the code coverage plugin:

module.exports = (on, config) => {
  on('task', require('@cypress/code-coverage/task'));
  // Other Cypress configuration here
};

With this setup, run your Cypress tests as usual, and code coverage reports will be generated in the coverage directory.

3. NPX (Node.js, JavaScript, TypeScript)

NPX is a package runner tool that comes with Node.js. It can be used to execute packages from the npm registry without having to install them globally or locally. One such package is nyc, which provides code coverage for Node.js, JavaScript, and TypeScript applications.

Features:

• Works with Node.js, JavaScript, and TypeScript applications.
• It can be used with any test runner, making it versatile and flexible.
• Command-line integration with NPX allows you to avoid global or local installations.
• Supports multiple report formats, including text, HTML, and JSON.
• Easily configurable through a nyc configuration file (.nycrc or package.json).
• Integration with Continuous Integration (CI) platforms for automated coverage reporting.

Installation

First, you need to install nyc globally or locally in your project:

npm install --save-dev nyc

You can then use NPX to run your tests with code coverage like this:

npx nyc mocha test.js

Replace mocha test.js with your testing command. nyc will generate code coverage reports in the ./coverage directory by default.

Conclusion

While we don't rank these tools in terms of popularity, each tool serves a specific purpose. One may excel in unit testing, while another may be more suitable for testing enterprise-grade applications but not as well-suited for more straightforward tests. The choice of a tool ultimately depends on your project's objectives.

In summary, a higher coverage percentage indicates more thorough app testing. If it reaches 100 percent, every aspect has been tested, resulting in a comprehensively tested app. We hope you find this post informative and valuable.