### Question:
MetaRangeImpl implements MetaRange { @Override public CompletableFuture<Boolean> create(StreamProperties streamProps) { return executeTask((future) -> unsafeCreate(future, streamProps)); } MetaRangeImpl(MVCCAsyncStore<byte[], byte[]> store,
                         ExecutorService executor,
                         StorageContainerPlacementPolicy placementPolicy); private  MetaRangeImpl(MVCCAsyncStore<byte[], byte[]> store,
                          ExecutorService executor,
                          StorageContainerPlacementPolicy placementPolicy,
                          NavigableMap<Long, RangeMetadata> ranges,
                          List<Long> currentRanges,
                          StreamMetadata meta,
                          long cTime,
                          long mTime); static final byte[] getStreamMetadataKey(long streamId); static final byte[] getStreamRangeKey(long streamId, long rangeId); static final byte[] getStreamMetadataEndKey(long streamId); static final boolean isMetadataKey(byte[] key); @VisibleForTesting long unsafeGetCreationTime(); @VisibleForTesting long unsafeGetModificationTime(); @VisibleForTesting LifecycleState unsafeGetLifecycleState(); @VisibleForTesting synchronized StreamProperties unsafeGetStreamProperties(); @VisibleForTesting synchronized long unsafeGetStreamId(); @VisibleForTesting NavigableMap<Long, RangeMetadata> unsafeGetRanges(); @VisibleForTesting List<Long> unsafeGetCurrentRanges(); @Override synchronized String getName(); @Override CompletableFuture<Boolean> create(StreamProperties streamProps); @Override CompletableFuture<MetaRange> load(long streamId); @Override CompletableFuture<Boolean> delete(long streamId); @Override CompletableFuture<ServingState> getServingState(); @Override CompletableFuture<ServingState> updateServingState(ServingState state); @Override CompletableFuture<StreamConfiguration> getConfiguration(); @Override CompletableFuture<List<RangeMetadata>> getActiveRanges();  }### Answer:
@Test public void testCreate() throws Exception { assertTrue(FutureUtils.result(this.metaRange.create(streamProps))); verifyStreamMetadata(metaRange, streamProps); }
@Test public void testDoubleCreate() throws Exception { assertTrue(FutureUtils.result(this.metaRange.create(streamProps))); assertIllegalStateException(this.metaRange.create(streamProps)); }