@Override
    public ContainerBuildPlan extendContainerBuildPlan(
        ContainerBuildPlan buildPlan,
        Map<String, String> properties,
        Optional<T> extraConfig,
        MavenData mavenData,
        ExtensionLogger logger)
        throws JibPluginExtensionException {
      return extensionBody.extendContainerBuildPlan(
          buildPlan, properties, extraConfig, mavenData, logger);
    }
Plugin extension test for {@link MavenProjectProperties}.
jib-maven-plugin/src/test/java/com/google/cloud/tools/jib/maven/MavenProjectPropertiesExtensionTest.java