### Question:
ResourceChangeInfo { public void updateHashForGroup(final String hash, final String groupName) { notNull(groupName); this.currentHash = hash; if (isChangedHash()) { LOG.debug("Group {} has changed", groupName); groups.clear(); } }  void updateHashForGroup(final String hash, final String groupName); void reset(); boolean isChanged(final String groupName); boolean isCheckRequiredForGroup(final String groupName); @Override String toString();  }### Answer:
@Test(expected = NullPointerException.class) public void cannotUpdateHashForNullGroup() { victim.updateHashForGroup("", null); }