Problem: JaCoCo - Skipping JaCoCo execution due to missing execution data file

When configured JaCoCo with maven project, it is very common to meet the problem "Skipping JaCoCo execution due to missing execution data file" when running the test. It is not an error, the build will still succeed, however, the JaCoCo will not generate the report because it could not find the Jacobo.exec file.

There are many reasons for this problem. But most common case is that the JaCoCo agent is failed to configured into the command line. Using the command "mvn -X clean verify" to check on the debug logs. At the "TESTS" step, you will be able to see a line for "Forking command line".

If the JaCoCo agent is configured correctly, you will be able to see similar logs as below.

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 T E S T S

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 T E S T S

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[DEBUG] boot classpath:  /Users/jhuang8/.m2/raptor2/org/apache/maven/surefire/surefire-booter/2.17/surefire-booter-2.17.jar  /Users/jhuang8/.m2/raptor2/org/apache/maven/surefire/surefire-api/2.17/surefire-api-2.17.jar  /Users/jhuang8/Documents/workspace/JaCoCoPractice/target/test-classes  /Users/jhuang8/Documents/workspace/JaCoCoPractice/target/classes  /Users/jhuang8/.m2/raptor2/junit/junit/4.8.1/junit-4.8.1.jar  /Users/jhuang8/.m2/raptor2/org/apache/maven/surefire/surefire-junit4/2.17/surefire-junit4-2.17.jar

[DEBUG] boot(compact) classpath:  surefire-booter-2.17.jar  surefire-api-2.17.jar  test-classes  classes  junit-4.8.1.jar  surefire-junit4-2.17.jar

Forking command line: /bin/sh -c cd /Users/jhuang8/Documents/workspace/JaCoCoPractice && /Library/Java/JavaVirtualMachines/jdk1.8.0_144.jdk/Contents/Home/jre/bin/java -javaagent:/Users/jhuang8/.m2/raptor2/org/jacoco/org.jacoco.agent/0.7.6.201602180812/org.jacoco.agent-0.7.6.201602180812-runtime.jar=destfile=/Users/jhuang8/Documents/workspace/JaCoCoPractice/target/jacoco.exec -Xmx1024m -XX:MaxPermSize=512m -jar /Users/jhuang8/Documents/workspace/JaCoCoPractice/target/surefire/surefirebooter3359878682012651006.jar /Users/jhuang8/Documents/workspace/JaCoCoPractice/target/surefire/surefire8553706350128891199tmp /Users/jhuang8/Documents/workspace/JaCoCoPractice/target/surefire/surefire_04828513279405888630tmp

The JaCoCo part is flagged out as blue.

And how can we add in these JaCoCo agent info? according to the office site Jacobo:prepare-agent,  you can obviously add in the @{argLine} at your maven-surefire-plugin configurations as

<plugin>

   <artifactId>maven-surefire-plugin</artifactId>

   <configuration>

      <forkMode>once</forkMode>

      <forkCount>1</forkCount>

      <argLine>@{argLine} -Xmx1024m </argLine>

      <reuseForks>false</reuseForks>

   </configuration>

</plugin>

The default name is argLine, but sometime, the JaCoCo configuration will be overwrote by some other argLine setup or plugin in pom. A way to avoid this is to configure a new property name at JaCoCo plugin and put it at the maven-surefire-plugin. Below is the sample configruation.

Set a new propertyName at JaCoCo plugin

<plugin>

   <groupId>org.jacoco</groupId>

   <artifactId>jacoco-maven-plugin</artifactId>

   <version>0.7.6.201602180812</version>

   <executions>

<execution>

<id>prepare-agent</id>

<goals>

         <goal>prepare-agent</goal>

</goals>  

<configuration>

<propertyName>jaCoCoArgLine</propertyName>

      </configuration>

</execution>

<execution>

<id>post-unit-test</id>

<phase>test</phase>

<goals>

<goal>report</goal>

</goals>

</execution>

   </executions>

</plugin>

and put the new propertyName at maven-surefire-plugin like below

<argLine>jaCoCoArgLine -Xmx1024m </argLine>

This time, check at the maven logs, it will shows as jaCoCoArgline under JaCoCo maven plugin for prepare-agent stage. And you will be able to see the Jacobo.exec file generated under that path.

[INFO] --- jacoco-maven-plugin:0.7.6.201602180812:prepare-agent (prepare-agent) @ JaCoCoPractice ---

[INFO] jaCoCoArgLine set to -javaagent:/Users/jhuang8/.m2/raptor2/org/jacoco/org.jacoco.agent/0.7.6.201602180812/org.jacoco.agent-0.7.6.201602180812-runtime.jar=destfile=/Users/jhuang8/Documents/workspace/JaCoCoPractice/target/jacoco.exec

If the problem still shows up, then double check the maven-surefire-plugin, according to official site Maven Plug-in it has the restrictions as below.

When using the maven-surefire-plugin or maven-failsafe-plugin you must not use a forkCount of 0 or set the forkMode to never as this would prevent the execution of the tests with the javaagentset and no coverage would be recorded.