@Override
    synchronized Set<TopicPartition> partitions() {
        return wrapped.partitions();
    }
@Test
    public void testPartitions() {
        final Set<TopicPartition> partitions = Collections.singleton(new TopicPartition("topic", 0));
        when(wrapped.partitions()).thenReturn(partitions);

        final Set<TopicPartition> result = synchronizedPartitionGroup.partitions();

        assertEquals(partitions, result);
        verify(wrapped, times(1)).partitions();
    }