### Question:
TopologyBuilder { public synchronized Set<String> sourceTopics(String applicationId) { Set<String> topics = new HashSet<>(); for (String topic : sourceTopicNames) { if (internalTopicNames.contains(topic)) { topics.add(applicationId + "-" + topic); } else { topics.add(topic); } } return Collections.unmodifiableSet(topics); } TopologyBuilder(); synchronized final TopologyBuilder addSource(String name, String... topics); synchronized final TopologyBuilder addSource(String name, Deserializer keyDeserializer, Deserializer valDeserializer, String... topics); synchronized final TopologyBuilder addSink(String name, String topic, String... parentNames); synchronized final TopologyBuilder addSink(String name, String topic, StreamPartitioner partitioner, String... parentNames); synchronized final TopologyBuilder addSink(String name, String topic, Serializer keySerializer, Serializer valSerializer, String... parentNames); synchronized final TopologyBuilder addSink(String name, String topic, Serializer<K> keySerializer, Serializer<V> valSerializer, StreamPartitioner<K, V> partitioner, String... parentNames); synchronized final TopologyBuilder addProcessor(String name, ProcessorSupplier supplier, String... parentNames); synchronized final TopologyBuilder addStateStore(StateStoreSupplier supplier, boolean isInternal, String... processorNames); synchronized final TopologyBuilder addStateStore(StateStoreSupplier supplier, String... processorNames); synchronized final TopologyBuilder connectProcessorAndStateStores(String processorName, String... stateStoreNames); synchronized final TopologyBuilder connectProcessors(String... processorNames); synchronized final TopologyBuilder addInternalTopic(String topicName); synchronized Map<Integer, TopicsInfo> topicGroups(String applicationId); synchronized Map<Integer, Set<String>> nodeGroups(); synchronized final TopologyBuilder copartitionSources(Collection<String> sourceNodes); synchronized Collection<Set<String>> copartitionGroups(); synchronized ProcessorTopology build(String applicationId, Integer topicGroupId); synchronized Set<String> sourceTopics(String applicationId);  }### Answer:
@Test public void testSourceTopics() { final TopologyBuilder builder = new TopologyBuilder(); builder.addSource("source-1", "topic-1"); builder.addSource("source-2", "topic-2"); builder.addSource("source-3", "topic-3"); builder.addInternalTopic("topic-3"); Set<String> expected = new HashSet<String>(); expected.add("topic-1"); expected.add("topic-2"); expected.add("X-topic-3"); assertEquals(expected, builder.sourceTopics("X")); }