### Question:
DataSetRepository { boolean dataSetExists(String ownerId, String dataSet) { return unsafeGetDataSetWithoutCheckingPermissions(ownerId, dataSet).isPresent(); } DataSetRepository(ExecutorService executorService, PermissionFetcher permissionFetcher,
                           BdbEnvironmentCreator dataStoreFactory,
                           TimbuctooRdfIdHelper rdfIdHelper, Consumer<String> onUpdated,
                           boolean publicByDefault, DataStorage dataStorage); void reloadDataSet(String dataSetId); Optional<DataSet> getDataSet(User user, String ownerId, String dataSetId); Optional<DataSet> unsafeGetDataSetWithoutCheckingPermissions(String ownerId, String dataSetId); boolean userMatchesPrefix(User user, String prefix); DataSet createDataSet(User user, String dataSetId); DataSet createDataSet(User user, String dataSetId,
                               List<ImportInfo> importInfos); void publishDataSet(User user, String ownerId, String dataSetName); Collection<DataSet> getDataSets(); Collection<DataSet> getPromotedDataSets(); Collection<DataSet> getDataSetsWithWriteAccess(User user); Collection<DataSet> getDataSetsWithReadAccess(@Nullable User user); void removeDataSet(String ownerId, String dataSetName, User user); void stop(); void start(); void subscribeToDataSetsUpdated(Runnable dataSetsUpdatedListener);  }### Answer:
@Test public void dataSetExistsReturnsFalseIfTheUserIsNotKnown() { boolean dataSetExists = dataSetRepository.dataSetExists("ownerid", "dataset_id"); assertThat(dataSetExists, is(false)); }