### Question:
ResourceChangeInfo { public boolean isChanged(final String groupName) { notNull(groupName); final boolean result = isChangedHash() ? true : !groups.contains(groupName); if (result) { groups.add(groupName); } return result; }  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 cannotCheckChangeForNullGroupName() { victim.isChanged(null); }
@Test public void shouldDetectChangeByDefault() { assertTrue(victim.isChanged(GROUP1_NAME)); assertFalse(victim.isChanged(GROUP1_NAME)); }