jacoco only shows coverage for classes in the same module

Question

I have a somewhat large multi-module Maven project. I have the unit tests in each module being processed by Jacoco. I have a separate child module doing "merge" and "report-aggregate", and this appears to be generating data. I'm even using the generated data in SonarQube. Most of my tests are using PowerMock, and I'm using offline instrumentation.

However, after looking closer at the coverage data, I see that it is leaving out coverage data for classes and methods that I know are being executed during tests. The pattern I see in every module is that it only reports coverage for a single class in each module, which is a class actually in the current module. Almost all of the tests also call out to other classes in other modules in the build, and coverage for those classes are never reported.

The following plugin configurations are in the parent pom used by each child module:

<plugin>
    <groupId>org.jacoco</groupId>
    <artifactId>jacoco-maven-plugin</artifactId>
    <version>0.7.8</version>
    <executions>
        <execution>
            <id>default-instrument</id>
            <goals>
                <goal>instrument</goal>
            </goals>
        </execution>
        <execution>
            <id>default-restore-instrumented-classes</id>
            <goals>
                <goal>restore-instrumented-classes</goal>
            </goals>
        </execution>
        <execution>
            <id>default-report</id>
            <phase>prepare-package</phase>
            <goals>
                <goal>report</goal>
            </goals>
        </execution>
    </executions>
</plugin>
<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-surefire-plugin</artifactId>
    <version>2.19.1</version>
    <configuration>
        <argLine>-Xmx1024m</argLine>
        <includes>
            <include>**/*Test.java</include>
        </includes>
        <systemPropertyVariables>
            <jacoco-agent.destfile>${project.build.directory}/jacoco.exec</jacoco-agent.destfile>
            <running-unit-test>true</running-unit-test>
        </systemPropertyVariables>
    </configuration>
</plugin>

When I inspect the generated HTML results for each module, I find that it only reports results for the single class in the current module, and not the data for classes in other modules. From this, I would assume that how I do "merge" and "report-aggregate" in the separate child module is probably irrelevant to this problem.

The generated "jacoco.exec" file is binary, but I tried "catting" out one from one module just to see what ascii text was visible, and it showed only one occurrence of anything that looked like a file name, and it was the only file name reported in the HTML coverage report for that module.

I'm not sure what other information I can report.

Update:

I guess I can see pretty clearly now that when surefire runs unit tests, it uses the instrumented classes from the current module, but the uninstrumented classes from the maven artifacts. This is why I only see coverage for classes in the current module.

So it seems like I need a way to specify that the "target/generated-classes/jacoco" folder for each module the current module depends on, is prepended to the classpath that surefire uses. I don't see a way to do that.

Alternatively, I see that the "instrument" goal has an "includes" configuration element. Should I be specifying paths to all of the "target/classes" directories for each of the modules that the current module depends on?

Answer 1

Recording of code coverage for some class requires its instrumentation. Goal instrument performs instrumentation of classes of current module.

all of the tests also call out to other classes in other modules

so the ones that are not instrumented. And if I correctly understood, then exactly those for which you are missing coverage.

If you don't use PowerMock for classes that come from other modules, but only for classes in current module, then you can combine offline instrumentation with on-the-fly using agent. But in this case make sure that classes instrumented offline are explicitly excluded from instrumentation by agent, otherwise agent will be throwing IllegalStateException: Class ... is already instrumented.

If you use PowerMock for classes that come from other modules, then this becomes more complex due to strictness of Maven in regards of manipulations with classpaths and dependencies. And I doubt that this can be easily achieved using one mvn comand, however seems possible using more:

1. instrument and run tests, but don't use restore-instrumented-classes
2. restore classes and generate report(s)

Unfortunately you haven't provided complete example (https://stackoverflow.com/help/mcve) and I don't have time to prepare full example to test this approach right now.

As a side note: inability to simply use agent comes from the fact that PowerMock bypasses any agent and reads class files from disk.