### Question:
JibPluginConfiguration extends AbstractMojo { Set<String> getTargetImageAdditionalTags() { String property = getProperty(PropertyNames.TO_TAGS); List<String> tags = property != null ? ConfigurationPropertyValidator.parseListProperty(property) : to.tags; if (tags.stream().anyMatch(Strings::isNullOrEmpty)) { String source = property != null ? PropertyNames.TO_TAGS : "<to><tags>"; throw new IllegalArgumentException(source + " has empty tag"); } return new HashSet<>(tags); }  String getContainerizingMode();  }### Answer:
@Test public void testEmptyOrNullTags() { sessionProperties.put("jib.to.tags", "a,,b"); try { testPluginConfiguration.getTargetImageAdditionalTags(); Assert.fail(); } catch (IllegalArgumentException ex) { Assert.assertEquals("jib.to.tags has empty tag", ex.getMessage()); } }