@Test
  public void testGetChildValue_nullValue() {
    Xpp3Dom root = new Xpp3Dom("root");
    addXpp3DomChild(root, "foo", null);

    assertThat(MavenProjectProperties.getChildValue(root)).isEmpty();
    assertThat(MavenProjectProperties.getChildValue(root, "foo")).isEmpty();
  }
Helper for reading back layers in a {@link BuildContext}.
jib-maven-plugin/src/test/java/com/google/cloud/tools/jib/maven/MavenProjectPropertiesTest.java