// modelVersion is neither inherited nor injected
    @Test
    void testMergeModel_ModelVersion() {
        Model parent = Model.newBuilder().modelVersion("4.0.0").build();
        Model model = Model.newInstance();
        Model.Builder builder = Model.newBuilder(model);
        modelMerger.mergeModel_ModelVersion(builder, model, parent, false, null);

<?xml version="1.0"?><project>
  <parent>
    <artifactId>wagon</artifactId>
    <groupId>org.apache.maven.wagon</groupId>
    <version>1.0-beta-2</version>
  </parent>
  <modelVersion>4.0.0</modelVersion>
  <artifactId>wagon-provider-api</artifactId>
  <name>Maven Wagon API</name>
  <version>1.0-beta-2</version>
  <description>Maven Wagon API that defines the contract between different Wagon implementations</description>
  <dependencies>

<project>
  <modelVersion>4.0.0</modelVersion>
  <groupId>commons-logging</groupId>
  <artifactId>commons-logging</artifactId>
  <name>Logging</name>
  <version>1.0.3</version>
  <description>Commons Logging</description>
  <url>http://jakarta.apache.org/commons/logging/</url>
  <inceptionYear>2001</inceptionYear>
  <build />
  <dependencies>
    <dependency>
      <groupId>log4j</groupId>
      <artifactId>log4j</artifactId>

 utilized across all your Maven projects.

+-----+
 m0 <- m1 <- m2
+-----+

 which is transformed into

+-----+
 super model <- m0 <- m1 <- m2
+-----+

+-----+
<project>
 <modelVersion>4.0.0</modelVersion>
 <parent>
   <groupId></groupId>
   <artifactId></artifactId>
   <version></version>
 </parent>
</project>
+-----+

Extending the POM in the future

<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>

  <parent>
    <groupId>org.hamcrest</groupId>
    <artifactId>hamcrest-parent</artifactId>
    <version>1.3</version>
  </parent>

  <artifactId>hamcrest-core</artifactId>

<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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <parent>
    <artifactId>plexus-components</artifactId>
    <groupId>org.codehaus.plexus</groupId>
    <version>1.1.6</version>
  </parent>

  <artifactId>plexus-active-collections</artifactId>

-->
<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.apache.maven</groupId>
    <artifactId>maven-api</artifactId>
    <version>4.0.0-beta-1-SNAPSHOT</version>
  </parent>

  <artifactId>maven-api-spi</artifactId>

  <parent>
    <artifactId>wagon</artifactId>
    <groupId>org.apache.maven.wagon</groupId>
    <version>1.0-beta-2</version>
  </parent>
  <modelVersion>4.0.0</modelVersion>
  <artifactId>wagon-providers</artifactId>
  <packaging>pom</packaging>
  <name>Maven Wagon Providers Parent</name>
  <modules>
    <module>wagon-file</module>
    <module>wagon-ftp</module>

-->

<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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-surefire-plugin</artifactId>
  <version>0.1</version>
  <packaging>maven-plugin</packaging>

-->

<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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>org.apache.maven.its.plugins</groupId>
  <artifactId>maven-it-plugin</artifactId>
  <version>0.1</version>
  <packaging>maven-plugin</packaging>

  <name>Maven Integration Test Plugin</name>