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[[jacoco_plugin]]
= The JaCoCo Plugin

The JaCoCo plugin provides code coverage metrics for Java code via integration with https://www.jacoco.org/jacoco/[JaCoCo].

[[sec:jacoco_getting_started]]
== Getting Started

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

====
include::sample[dir="snippets/reference/core-plugins/jacoco-quickstart/kotlin",files="build.gradle.kts[tags=apply-plugin]"]
include::sample[dir="snippets/reference/core-plugins/jacoco-quickstart/groovy",files="build.gradle[tags=apply-plugin]"]
====

If the Java plugin is also applied to your project, a new task named `jacocoTestReport` is created.
By default, an HTML report is generated at `layout.buildDirectory.dir("reports/jacoco/test/html")`.

NOTE: While tests should be executed before generation of the report, the `jacocoTestReport` task does not depend on the `test` task.

Depending on your usecases, you may want to always generate the `jacocoTestReport` or run the `test` task before generating the report explicitly.

====
include::sample[dir="snippets/reference/core-plugins/jacoco-quickstart/kotlin",files="build.gradle.kts[tags=testtask-dependency]"]
include::sample[dir="snippets/reference/core-plugins/jacoco-quickstart/groovy",files="build.gradle[tags=testtask-dependency]"]
====

[[sec:configuring_the_jacoco_plugin]]
== Configuring the JaCoCo Plugin

The JaCoCo plugin adds a project extension named `jacoco` of type link:{groovyDslPath}/org.gradle.testing.jacoco.plugins.JacocoPluginExtension.html[JacocoPluginExtension], which allows configuring defaults for JaCoCo usage in your build.

====
include::sample[dir="snippets/reference/core-plugins/jacoco-quickstart/kotlin",files="build.gradle.kts[tags=jacoco-configuration]"]
include::sample[dir="snippets/reference/core-plugins/jacoco-quickstart/groovy",files="build.gradle[tags=jacoco-configuration]"]
====

.Gradle defaults for JaCoCo properties
[%header%autowidth,compact]
|===
| Property | Gradle default
| toolVersion | `0.8.14`
| reportsDirectory | `layout.buildDirectory.dir("reports/jacoco")`
|===

[[sec:jacoco_report_configuration]]
== JaCoCo Report configuration

The link:{groovyDslPath}/org.gradle.testing.jacoco.tasks.JacocoReport.html[JacocoReport] task can be used to generate code coverage reports in different formats. It implements the standard Gradle type link:{groovyDslPath}/org.gradle.api.reporting.Reporting.html[Reporting] and exposes a report container of type link:{javadocPath}/org/gradle/testing/jacoco/tasks/JacocoReportsContainer.html[JacocoReportsContainer].

====
include::sample[dir="snippets/reference/core-plugins/jacoco-quickstart/kotlin",files="build.gradle.kts[tags=report-configuration]"]
include::sample[dir="snippets/reference/core-plugins/jacoco-quickstart/groovy",files="build.gradle[tags=report-configuration]"]
====

image::jacocoHtmlReport.png[JaCoCo HTML report,903,277]

[[sec:jacoco_report_violation_rules]]
== Enforcing code coverage metrics

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

The link:{groovyDslPath}/org.gradle.testing.jacoco.tasks.JacocoCoverageVerification.html[JacocoCoverageVerification] task can be used to verify if code coverage metrics are met based on configured rules. Its API exposes the method link:{javadocPath}/org/gradle/testing/jacoco/tasks/JacocoCoverageVerification.html#violationRules-org.gradle.api.Action-[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 link:{javadocPath}/org/gradle/testing/jacoco/tasks/rules/JacocoViolationRulesContainer.html[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.

====
include::sample[dir="snippets/reference/core-plugins/jacoco-quickstart/kotlin",files="build.gradle.kts[tags=violation-rules-configuration]"]
include::sample[dir="snippets/reference/core-plugins/jacoco-quickstart/groovy",files="build.gradle[tags=violation-rules-configuration]"]
====

The link:{groovyDslPath}/org.gradle.testing.jacoco.tasks.JacocoCoverageVerification.html[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.

[[sec:jacoco_specific_task_configuration]]
== JaCoCo specific task configuration

The JaCoCo plugin adds a link:{groovyDslPath}/org.gradle.testing.jacoco.plugins.JacocoTaskExtension.html[JacocoTaskExtension] extension to all tasks of type link:{groovyDslPath}/org.gradle.api.tasks.testing.Test.html[Test]. This extension allows the configuration of the JaCoCo specific properties of the test task.

====
include::sample[dir="snippets/reference/core-plugins/jacoco-quickstart/kotlin",files="build.gradle.kts[tags=testtask-configuration]"]
include::sample[dir="snippets/reference/core-plugins/jacoco-quickstart/groovy",files="build.gradle[tags=testtask-configuration]"]
====

[NOTE]
====
Tasks configured for running with the JaCoCo agent delete the destination file for the execution data when the task starts executing.
This ensures that no stale coverage data is present in the execution data.
====

[[sec:jacoco_task_extension_default_values]]
=== Default values of the JaCoCo Task extension

====
include::sample[dir="snippets/reference/core-plugins/jacoco-quickstart/kotlin",files="build.gradle.kts[tags=testtask-configuration-defaults]"]
include::sample[dir="snippets/reference/core-plugins/jacoco-quickstart/groovy",files="build.gradle[tags=testtask-configuration-defaults]"]
====

While all tasks of type link:{groovyDslPath}/org.gradle.api.tasks.testing.Test.html[Test] are automatically enhanced to provide coverage information when the `java` plugin has been applied, any task that implements link:{javadocPath}/org/gradle/process/JavaForkOptions.html[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:

====
include::sample[dir="snippets/reference/core-plugins/jacoco-application/kotlin",files="build.gradle.kts[tags=application-configuration]"]
include::sample[dir="snippets/reference/core-plugins/jacoco-application/groovy",files="build.gradle[tags=application-configuration]"]
====

[source,text]
----
.
└── build
    ├── jacoco
    │   └── run.exec
    └── reports
        └── jacoco
            └── applicationCodeCoverageReport
                └── html
                    └── index.html

----

[[sec:jacoco_tasks]]
== Tasks

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

`jacocoTestReport` — link:{groovyDslPath}/org.gradle.testing.jacoco.tasks.JacocoReport.html[JacocoReport]::
+
Generates code coverage report for the test task.

`jacocoTestCoverageVerification` — link:{groovyDslPath}/org.gradle.testing.jacoco.tasks.JacocoCoverageVerification.html[JacocoCoverageVerification]::
+
Verifies code coverage metrics based on specified rules for the test task.

[[sec:jacoco_dependency_management]]
== Dependency management

The JaCoCo plugin adds the following dependency configurations:

.JaCoCo plugin - dependency configurations
[%header%autowidth,compact]
|===
| Name          | Meaning

| `jacocoAnt`
| The JaCoCo Ant library used for running the `JacocoReport` and `JacocoCoverageVerification` tasks.

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

|===

[[sec:outgoing_variants_jacoco]]
== Outgoing Variants

When a project producing JaCoCo coverage data is applied alongside the <<jvm_test_suite_plugin#jvm_test_suite_plugin,JVM Test Suite Plugin>>, additional outgoing variants will be created.  These variants are designed for consumption by the <<jacoco_report_aggregation_plugin#jacoco_report_aggregation_plugin, JaCoCo Report Aggregation Plugin>>.

The attributes will resemble the following.  User-configurable attributes are highlighted below the sample.

[source,text]
----
--------------------------------------------------
Variant coverageDataElementsForTest (i)
--------------------------------------------------
Binary results containing Jacoco test coverage for all targets in the 'test' Test Suite.

Capabilities
    - org.gradle.sample:application:1.0.2 (default capability)
Attributes
    - org.gradle.category         = verification
    - org.gradle.testsuite.name   = test           // <1>
    - org.gradle.verificationtype = jacoco-coverage

Artifacts
    - build/jacoco/test.exec (artifactType = binary)
----
<1> TestSuiteName attribute; value is derived from link:{javadocPath}/org/gradle/testing/base/TestSuite.html#getName--[TestSuite#getName()].
