@Test
  public void testRunPluginExtensions_extensionDefinedConfigurations()
      throws JibPluginExtensionException {
    FooExtension fooExtension =
        new FooExtension(
            (buildPlan, properties, extraConfig, mavenData, logger) -> {
              Assert.assertEquals("fooParamValue", extraConfig.get().fooParam);
              return buildPlan;
            });
    BarExtension barExtension =
        new BarExtension(
            (buildPlan, properties, extraConfig, mavenData, logger) -> {
              Assert.assertEquals("barParamValue", extraConfig.get().barParam);
              return buildPlan;
            });
    loadedExtensions = Arrays.asList(fooExtension, barExtension);

    mavenProjectProperties.runPluginExtensions(
        Arrays.asList(
            new FooExtensionConfig(new ExtensionDefinedFooConfig("fooParamValue")),
            new BarExtensionConfig(new ExtensionDefinedBarConfig("barParamValue"))),
        containerBuilder);
  }
Plugin extension test for {@link MavenProjectProperties}.
jib-maven-plugin/src/test/java/com/google/cloud/tools/jib/maven/MavenProjectPropertiesExtensionTest.java