AdderUsageObserver.setUsed( false );
Source source = new Source();
source.setPets( Arrays.asList( "mouse" ) );
Target target = new Target();
target.setPets( new ArrayList<Long>( Arrays.asList( 1L ) ) );
SourceTargetMapper.INSTANCE.toExistingTarget( source, target );
assertThat( target ).isNotNull();
assertThat( target.getPets().size() ).isEqualTo( 2 );
assertThat( target.getPets().get( 0 ) ).isEqualTo( 1L );
assertThat( target.getPets().get( 1 ) ).isEqualTo( 2L );
assertTrue( AdderUsageObserver.isUsed() );
}