Cross-module code coverage with Jacoco offline instrumentation in gradle mutlimodule project

SergiiGnatiuk :

I have to use Jacoco offline instrumentation in my project because there is PowerMock that is used as well.

The issue description: suppose you have gradle project with two modules: A, B. Module A has tests that cover a code from the module B. On code coverage data collection I figured out that coverage data(should be provided by the module A) for the module B is completely missed.

I've created a test project that demonstrates the issue: https://github.com/SurpSG/jacoco-offline-instrumentation

Jacoco offline instrumentation setup for gradle project is based on the answer https://stackoverflow.com/a/42238982/2689114

On the other hand, when I'm using jacoco gradle plugin I can observe that coverage data provided by module A for module B successfully collected to a summary report. I've created one more test project to demonstrate this: https://github.com/SurpSG/jacoco-gradle-plugin-merge-coverage

Am I have a wrong setup for the gradle multimodule project + jacoco offline instrumentation?

SergiiGnatiuk :

After some investigation, I figured out that modules dependencies in Gradle are resolved via .jar files:

<dependent-module>.classpath contains <dependency-module>.jar

So, in my case, I need to build some special jar that contains instrumented classes.

Instrumenting classes

task preprocessClassesForJacoco(dependsOn: ['classes']) {
        ext.outputDir = buildDir.path + '/classes-instrumented'
        doLast {
            ant.taskdef(name: 'instrument',
                    classname: 'org.jacoco.ant.InstrumentTask',
                    classpath: configurations.jacoco.asPath)
            ant.instrument(destdir: outputDir) {
                fileset(dir: sourceSets.main.java.outputDir, includes: '**/*.class', erroronmissingdir: false)
            }
        }
    }

The next step will be building instrumented jar:

task jacocoInstrumentedJar(type: Jar, dependsOn: [preprocessClassesForJacoco]) {
    baseName "${project.name}-instrumented"
    from preprocessClassesForJacoco.outputDir // path to instrumented classes
}

And finally, we need to replace the usual .jar with instrumented one

gradle.taskGraph.whenReady { graph ->
        if (graph.hasTask(preprocessClassesForJacoco)) {
            tasks.withType(Test) {
                doFirst {
                    ...
                    // getting a module dependencies
                    def modulesDependencies = moduleDependencies(project)
                    // removing regular jars
                    classpath -= files(modulesDependencies.jar.outputs.files)
                    // adding instrumented jars
                    classpath += files(modulesDependencies.jacocoInstrumentedJar.outputs.files)
                }
            }
        }
    }

I've updated the example project https://github.com/SurpSG/jacoco-offline-instrumentation with steps described above. Feel free to check out the project to try.