The JaCoCo Plugin - Gradle User Guide Version 4.3.1

# Chapter 64. The JaCoCo Plugin

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 = "0.7.9"
        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")
        }
    }

## 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.