maven - jacoco simple integration test solution

Question

I am following the standard Maven pattern where I use a separate module for integration tests. This module has a wrapper class that executes the major dependent jar project.

While the jar project has its own test cases, I am not interested in executing these. I want to see code coverage in the jar project when executed by the integration tests. Simple, no report aggregation.

Answer 1

Let me quote http://www.jacoco.org/jacoco/trunk/doc/report-aggregate-mojo.html even if its name contains a kind of "aggregation":

This also allows to create coverage reports when tests are in separate projects than the code under test, for example in case of integration tests.

Let's try. Given jar/src/main/java/example/Example.java:

package example;
public class Example {
  // to be covered by unit test
  public void a() {
    System.out.println("a");
  }

  // to be covered by integration test    
  public void b() {
    System.out.println("b");
  }
}

unit test jar/src/test/java/example/ExampleTest.java:

package example;
public class ExampleTest {
  @org.junit.Test
  public void test() {
    new Example().a();
  }
}

integration test it/src/test/java/example/ExampleITTest.java:

package example;
public class ExampleITTest {
  @org.junit.Test
  public void test() {
    new Example().b();
  }
}

pom.xml:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>

  <groupId>org.example</groupId>
  <artifactId>example</artifactId>
  <version>1.0-SNAPSHOT</version>
  <packaging>pom</packaging>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

  <modules>
    <module>jar</module>
    <module>it</module>
  </modules>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.8.2</version>
      <scope>test</scope>
    </dependency>
  </dependencies>

  <build>
    <plugins>
      <plugin>
        <groupId>org.jacoco</groupId>
        <artifactId>jacoco-maven-plugin</artifactId>
        <version>0.7.8</version>
        <executions>
          <execution>
            <goals>
              <goal>prepare-agent</goal>
              <goal>report</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>

</project>

jar/pom.xml:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <parent>
    <groupId>org.example</groupId>
    <artifactId>example</artifactId>
    <version>1.0-SNAPSHOT</version>
  </parent>

  <artifactId>jar</artifactId>

</project>

and finally most important part it/pom.xml where happens all the magic:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <parent>
    <groupId>org.example</groupId>
    <artifactId>example</artifactId>
    <version>1.0-SNAPSHOT</version>
  </parent>

  <artifactId>it</artifactId>

  <dependencies>
    <dependency>
      <groupId>org.example</groupId>
      <artifactId>jar</artifactId>
      <version>${project.version}</version>
    </dependency>
  </dependencies>

  <build>
    <plugins>
      <plugin>
        <groupId>org.jacoco</groupId>
        <artifactId>jacoco-maven-plugin</artifactId>
        <executions>
          <!--
          "report" goal can't cross boundaries of modules,
          while "report-aggregate" can, so let's use it, however
          by default it will load "jacoco.exec" from this module and from module "jar",
          so let's also change file name for this module to avoid intersection
          -->
          <execution>
            <configuration>
              <destFile>${project.build.directory}/jacoco-it.exec</destFile>
            </configuration>
          </execution>
          <execution>
            <id>it-report</id>
            <phase>verify</phase>
            <goals>
              <goal>report-aggregate</goal>
            </goals>
            <configuration>
              <dataFileIncludes>**/jacoco-it.exec</dataFileIncludes>
              <outputDirectory>${project.reporting.outputDirectory}/jacoco</outputDirectory>
            </configuration>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>
</project>

In such setup mvn clean verify will generate two reports - jar/target/site/jacoco showing that method a() is covered, and it/target/site/jacoco showing that method b() is covered.