Unit tests coverage using Jacoco for Scala

Question

When I using the follow structure on our Maven project:

<plugins>
        <plugin>
            <groupId>org.scala-tools</groupId>
            <artifactId>maven-scala-plugin</artifactId>
            <version>2.15.2</version>
            <executions>
                <execution>
                    <goals>
                        <goal>compile</goal>
                        <goal>testCompile</goal>
                    </goals>
                </execution>
            </executions>
            <configuration>
                <args>
                    <arg>-g:line</arg>
                </args>
            </configuration>
        </plugin>
        <plugin>
            <groupId>org.jacoco</groupId>
            <artifactId>jacoco-maven-plugin</artifactId>
            <version>0.5.8.201207111220</version>
            <executions>
                <execution>
                    <goals>
                        <goal>prepare-agent</goal>
                    </goals>
                </execution>
                <execution>
                    <id>report</id>
                    <phase>prepare-package</phase>
                    <goals>
                        <goal>report</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>

The tests are executed but the jacoco.exec file is not created. I tried to add this tag destFile to prepare-agent goal but have not success (the file with coverage information is not created).

Anyone have any form to calculate code coverage of unit test for Scala using maven and Jacoco?

Answer 1

Work of Jacoco maven plugin depends on versions of JDK, Scala and plugin itself.

Just added the same config and it works properly: both jacoco.exec and site/jacoco with reports are in the target dir: https://github.com/plokhotnyuk/calculator/commit/e3a84db02dd942b0df71d4fa337df29512e213f6

Then got agent failure when using latest (0.6.2.201302030002) version of Jacoco maven plugin:

Caused by: java.lang.RuntimeException: Class java/util/UUID could not be instrumented.
    at org.jacoco.agent.rt.internal_5d10cad.core.runtime.ModifiedSystemClassRuntime.createFor(ModifiedSystemClassRuntime.java:138)
    at org.jacoco.agent.rt.internal_5d10cad.core.runtime.ModifiedSystemClassRuntime.createFor(ModifiedSystemClassRuntime.java:99)
    at org.jacoco.agent.rt.internal_5d10cad.PreMain.createRuntime(PreMain.java:51)
    at org.jacoco.agent.rt.internal_5d10cad.PreMain.premain(PreMain.java:43)
    ... 6 more
Caused by: java.lang.NoSuchFieldException: $jacocoAccess
    at java.lang.Class.getField(Class.java:1542)
    at org.jacoco.agent.rt.internal_5d10cad.core.runtime.ModifiedSystemClassRuntime.createFor(ModifiedSystemClassRuntime.java:136)
    ... 9 more
FATAL ERROR in native method: processing of -javaagent failed
Exception in thread "main" 

And then the failure was worked out by switching from JDK8 to JDK7. Coverage report digits didn't changed.

Also after switching to Scala 2.10 source line highlighting started looks different:

Scala 2.9

Scala 2.10