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