Chapter 64. The JaCoCo Plugin

Table of Contents

64.1. Getting Started
64.2. Configuring the JaCoCo Plugin
64.3. JaCoCo Report configuration
64.4. Enforcing code coverage metrics
64.5. JaCoCo specific task configuration
64.6. Tasks
64.7. Dependency management

The JaCoCo plugin is currently incubating. Please be aware that the DSL and other configuration may change in later Gradle versions.

The JaCoCo plugin provides code coverage metrics for Java code via integration with JaCoCo.

64.1. Getting Started

To get started, apply the JaCoCo plugin to the project you want to calculate code coverage for.

Example 64.1. Applying the JaCoCo plugin

build.gradle

apply plugin: "jacoco"

If the Java plugin is also applied to your project, a new task named jacocoTestReport is created that depends on the test task. The report is available at $buildDir/reports/jacoco/test. By default, a HTML report is generated.

64.2. Configuring the JaCoCo Plugin

The JaCoCo plugin adds a project extension named jacoco of type JacocoPluginExtension, which allows configuring defaults for JaCoCo usage in your build.

Example 64.2. Configuring JaCoCo plugin settings

build.gradle

jacoco {
    toolVersion = "0.7.6.201602180812"
    reportsDir = file("$buildDir/customJacocoReportDir")
}

Table 64.1. Gradle defaults for JaCoCo properties

Property Gradle default

reportsDir

$buildDir/reports/jacoco

64.3. JaCoCo Report configuration

The JacocoReport task can be used to generate code coverage reports in different formats. It implements the standard Gradle type Reporting and exposes a report container of type JacocoReportsContainer.

Example 64.3. Configuring test task

build.gradle

jacocoTestReport {
    reports {
        xml.enabled false
        csv.enabled false
        html.destination file("${buildDir}/jacocoHtml")
    }
}

JaCoCo HTML report

64.4. Enforcing code coverage metrics

This feature requires the use of JaCoCo version 0.6.3 or higher.

The JacocoCoverageVerification task can be used to verify if code coverage metrics are met based on configured rules. Its API exposes the method JacocoCoverageVerification.violationRules(org.gradle.api.Action) which is used as main entry point for configuring rules. Invoking any of those methods returns an instance of JacocoViolationRulesContainer providing extensive configuration options. The build fails if any of the configured rules are not met. JaCoCo only reports the first violated rule.

Code coverage requirements can be specified for a project as a whole, for individual files, and for particular JaCoCo-specific types of coverage, e.g., lines covered or branches covered. The following example describes the syntax.

Example 64.4. Configuring violation rules

build.gradle

jacocoTestCoverageVerification {
    violationRules {
        rule {
            limit {
                minimum = 0.5
            }
        }

        rule {
            enabled = false
            element = 'CLASS'
            includes = ['org.gradle.*']

            limit {
                counter = 'LINE'
                value = 'TOTALCOUNT'
                maximum = 0.3
            }
        }
    }
}

Note: The code for this example can be found at samples/testing/jacoco/quickstart in the ‘-all’ distribution of Gradle.


The JacocoCoverageVerification task is not a task dependency of the check task provided by the Java plugin. There is a good reason for it. The task is currently not incremental as it doesn’t declare any outputs. Any violation of the declared rules would automatically result in a failed build when executing the check task. This behavior might not be desirable for all users. Future versions of Gradle might change the behavior.

64.5. JaCoCo specific task configuration

The JaCoCo plugin adds a JacocoTaskExtension extension to all tasks of type Test. This extension allows the configuration of the JaCoCo specific properties of the test task.

Example 64.5. Configuring test task

build.gradle

test {
    jacoco {
        append = false
        destinationFile = file("$buildDir/jacoco/jacocoTest.exec")
        classDumpDir = file("$buildDir/jacoco/classpathdumps")
    }
}

Table 64.2. Default values of the JaCoCo Task extension

Property Gradle default

enabled

true

destPath

$buildDir/jacoco

append

true

includes

[]

excludes

[]

excludeClassLoaders

[]

includeNoLocationClasses

false

sessionId

auto-generated

dumpOnExit

true

output

Output.FILE

address

-

port

-

classDumpPath

-

jmx

false

While all tasks of type Test are automatically enhanced to provide coverage information when the java plugin has been applied, any task that implements JavaForkOptions can be enhanced by the JaCoCo plugin. That is, any task that forks Java processes can be used to generate coverage information.

For example you can configure your build to generate code coverage using the application plugin.

Example 64.6. Using application plugin to generate code coverage data

build.gradle

apply plugin: "application"
apply plugin: "jacoco"

mainClassName = "org.gradle.MyMain"

jacoco {
    applyTo run
}

task applicationCodeCoverageReport(type:JacocoReport){
    executionData run
    sourceSets sourceSets.main
}

Note: The code for this example can be found at samples/testing/jacoco/application in the ‘-all’ distribution of Gradle.


Example 64.7. Coverage reports generated by applicationCodeCoverageReport

Build layout

application/
  build/
    jacoco/
      run.exec
    reports/jacoco/applicationCodeCoverageReport/html/
      index.html

64.6. Tasks

For projects that also apply the Java Plugin, The JaCoCo plugin automatically adds the following tasks:

Table 64.3. JaCoCo plugin - tasks

Task name Depends on Type Description

jacocoTestReport

-

JacocoReport

Generates code coverage report for the test task.

jacocoTestCoverageVerification

-

JacocoCoverageVerification

Verifies code coverage metrics based on specified rules for the test task.

64.7. Dependency management

The JaCoCo plugin adds the following dependency configurations:

Table 64.4. JaCoCo plugin - dependency configurations

Name Meaning

jacocoAnt

The JaCoCo Ant library used for running the JacocoReport, JacocoMerge and JacocoCoverageVerification tasks.

jacocoAgent

The JaCoCo agent library used for instrumenting the code under test.