@Nullable
  @Override
  public String getMainClassFromJarPlugin() {
    Plugin mavenJarPlugin = project.getPlugin("org.apache.maven.plugins:maven-jar-plugin");
    if (mavenJarPlugin != null) {
      return getChildValue(
              (Xpp3Dom) mavenJarPlugin.getConfiguration(), "archive", "manifest", "mainClass")
          .orElse(null);
    }
    return null;
  }
@Test
  public void testGetMainClassFromJar_missingManifest() {
    when(mockMavenProject.getPlugin("org.apache.maven.plugins:maven-jar-plugin"))
        .thenReturn(mockPlugin);
    when(mockPlugin.getConfiguration()).thenReturn(pluginConfiguration);
    pluginConfiguration.addChild(new Xpp3Dom("archive"));

    assertThat(mavenProjectProperties.getMainClassFromJarPlugin()).isNull();
  }