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[Jacoco] Aggregating Jacoco Reports for Multi-Module Projects

· 2 min read
Haril Song
Haril Song
Owner, Software Engineer at 42dot

Overview​

Starting from Gradle 7.4, a feature has been added that allows you to aggregate multiple Jacoco test reports into a single, unified report. In the past, it was very difficult to view the test results across multiple modules in one file, but now it has become much more convenient to merge these reports.

Usage​

Creating a Submodule Solely for Collecting Reports​

The current project structure consists of a module named application and other modules like list and utils that are used by the application module.

By adding a code-coverage-report module, we can collect the test reports from the application, list, and utils modules.

The project structure will then look like this:

  • application
  • utils
  • list
  • code-coverage-report

Adding the jacoco-report-aggregation Plugin​

// code-coverage-report/build.gradle
plugins {
    id 'base'
    id 'jacoco-report-aggregation'
}

repositories {
    mavenCentral()
}

dependencies {
    jacocoAggregation project(":application")
}

Now, by running ./gradlew testCodeCoverageReport, you can generate a Jacoco report that aggregates the test results from all modules.

jacoco-directory

warning

To use the aggregation feature, a jar file is required. If you have set jar { enable = false }, you need to change it to true.

Update 22-09-28​

In the case of a Gradle multi-project setup, there is an issue where packages that were properly excluded in a single project are not excluded in the aggregate report.

By adding the following configuration, you can generate a report that excludes specific packages.

testCodeCoverageReport {
    reports {
        csv.required = true
        xml.required = false
    }
    getClassDirectories().setFrom(files(
        [project(':api'), project(':utils'), project(':core')].collect {
            it.fileTree(dir: "${it.buildDir}/classes/java/main", exclude: [
                '**/dto/**',
                '**/config/**',
                '**/output/**',
            ])
        }
    ))
}

Next Step​

The jvm-test-suite plugin, which is introduced alongside jacoco-aggregation-report in Gradle, also seems very useful. Since these plugins are complementary, it would be beneficial to use them together.

Reference​