/**
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements. See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership. The ASF licenses this file
    * to you under the Apache License, Version 2.0 (the
    * "License"); you may not use this file except in compliance
    * with the License.  You may obtain a copy of the License at
    *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.commons.rdf.api;
  
  import static org.junit.Assert.*;
  
  import java.util.ArrayList;
  import java.util.HashSet;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Locale;
  import java.util.Map;
  import java.util.Optional;
  import java.util.Set;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.stream.Collectors;
  import java.util.stream.Stream;
  
  import org.junit.Assume;
  import org.junit.Before;
  import org.junit.Test;
  
  /**
   * Test Dataset implementation
   * <p>
   * To add to your implementation's tests, create a subclass with a name ending
   * in <code>Test</code> and provide {@link #createFactory()} which minimally
   * must support {@link RDF#createDataset()} and {@link RDF#createIRI(String)}, but
   * ideally support all operations.
   * <p>
   * This test uses try-with-resources blocks for calls to {@link Dataset#stream()}
   * and {@link Dataset#iterate()}.
   *
   * @see Dataset
   * @see RDF
   */
  public abstract class AbstractDatasetTest {
  
      protected RDF factory;
      protected Dataset dataset;
      protected IRI alice;
      protected IRI bob;
      protected IRI name;
      protected IRI knows;
      protected IRI member;
      protected BlankNode bnode1;
      protected BlankNode bnode2;
      protected Literal aliceName;
      protected Literal bobName;
      protected Literal secretClubName;
      protected Literal companyName;
      protected Quad bobNameQuad;
      private IRI isPrimaryTopicOf;
      private IRI graph1;
      private BlankNode graph2;
  
      /**
       *
       * This method must be overridden by the implementing test to provide a
       * factory for the test to create {@link Dataset}, {@link IRI} etc.
       *
       * @return {@link RDF} instance to be tested.
       */
      protected abstract RDF createFactory();
  
      @Before
      public void createDatasetAndAdd() {
          factory = createFactory();
          dataset = factory.createDataset();
          assertEquals(0, dataset.size());
  
          graph1 = factory.createIRI("http://example.com/graph1");
          graph2 = factory.createBlankNode();
  
          alice = factory.createIRI("http://example.com/alice");
          bob = factory.createIRI("http://example.com/bob");
          name = factory.createIRI("http://xmlns.com/foaf/0.1/name");
          knows = factory.createIRI("http://xmlns.com/foaf/0.1/knows");
          member = factory.createIRI("http://xmlns.com/foaf/0.1/member");
          bnode1 = factory.createBlankNode("org1");
          bnode2 = factory.createBlankNode("org2");
  
          secretClubName = factory.createLiteral("The Secret Club");
          companyName = factory.createLiteral("A company");
         aliceName = factory.createLiteral("Alice");
         bobName = factory.createLiteral("Bob", "en-US");
 
         dataset.add(graph1, alice, name, aliceName);
         dataset.add(graph1, alice, knows, bob);
 
         dataset.add(graph1, alice, member, bnode1);
 
         bobNameQuad = factory.createQuad(graph2, bob, name, bobName);
         dataset.add(bobNameQuad);
 
         dataset.add(factory.createQuad(graph2, bob, member, bnode1));
         dataset.add(factory.createQuad(graph2, bob, member, bnode2));
         // NOTE: bnode1 used in both graph1 and graph2
         dataset.add(graph1, bnode1, name, secretClubName);
         dataset.add(graph2, bnode2, name, companyName);
 
         // default graph describes graph1 and graph2
         isPrimaryTopicOf = factory.createIRI("http://xmlns.com/foaf/0.1/isPrimaryTopicOf");
         dataset.add(null, alice, isPrimaryTopicOf, graph1);
         dataset.add(null, bob, isPrimaryTopicOf, graph2);
 
 
     }
 
     @Test
     public void size() throws Exception {
         assertEquals(10, dataset.size());
     }
 
     @Test
     public void iterate() throws Exception {
         Assume.assumeTrue(dataset.size() > 0);
         final List<Quad> quads = new ArrayList<>();
         for (final Quad t : dataset.iterate()) {
             quads.add(t);
         }
         assertEquals(dataset.size(), quads.size());
 
         //assertTrue(quads.contains(bobNameQuad));
         // java.util.List won't do any BlankNode mapping, so
         // instead bobNameQuad of let's check for an IRI-centric quad
         final Quad q = factory.createQuad(graph1, alice, name, aliceName);
         quads.contains(q);
 
         // aborted iteration
         final Iterable<Quad> iterate = dataset.iterate();
         final Iterator<Quad> it = iterate.iterator();
 
         assertTrue(it.hasNext());
         it.next();
         closeIterable(iterate);
 
         // second iteration - should start from fresh and
         // get the same count
         long count = 0;
         final Iterable<Quad> iterable = dataset.iterate();
         for (@SuppressWarnings("unused") final
         Quad t : iterable) {
             count++;
         }
         assertEquals(dataset.size(), count);
 
         // Pattern iteration which should cover multiple graphs.
 
         final Set<Quad> aliceQuads = new HashSet<>();
         for (final Quad aliceQ : dataset.iterate(null, alice, null, null)) {
             aliceQuads.add(aliceQ);
         }
         assertTrue(aliceQuads.contains(factory.createQuad(graph1, alice, name, aliceName)));
         assertTrue(aliceQuads.contains(factory.createQuad(graph1, alice, knows, bob)));
         // We can't test this by Quad equality, as bnode1 might become mapped by the
         // dataset
         //assertTrue(aliceQuads.contains(factory.createQuad(graph1, alice, member, bnode1)));
         assertTrue(aliceQuads.contains(factory.createQuad(null, alice, isPrimaryTopicOf, graph1)));
         assertEquals(4, aliceQuads.size());
 
         // Check the isPrimaryTopicOf statements in the default graph
         int topics = 0;
         for (final Quad topic : dataset.iterate(null, null, isPrimaryTopicOf, null)) {
             topics++;
             // COMMONSRDF-55: should not be <urn:x-arq:defaultgraph> or similar
             assertFalse(topic.getGraphName().isPresent());
         }
         assertEquals(2, topics);
     }
 
     @Test
     public void streamDefaultGraphNameAlice() throws Exception {
         // null below would match in ANY graph (including default graph)
         final Optional<? extends Quad> aliceTopic = dataset.stream(null, alice, isPrimaryTopicOf, null).findAny();
         assertTrue(aliceTopic.isPresent());
         // COMMONSRDF-55: should not be <urn:x-arq:defaultgraph> or similar
         assertNull(aliceTopic.get().getGraphName().orElse(null));
         assertFalse(aliceTopic.get().getGraphName().isPresent());
     }
 
 
     @Test
     public void streamDefaultGraphNameByPattern() throws Exception {
         // Explicitly select in only the default graph Optional.empty()
         final Optional<? extends Quad> aliceTopic = dataset.stream(Optional.empty(), null, null, null).findAny();
         assertTrue(aliceTopic.isPresent());
         // COMMONSRDF-55: should not be <urn:x-arq:defaultgraph> or similar
         assertNull(aliceTopic.get().getGraphName().orElse(null));
         assertFalse(aliceTopic.get().getGraphName().isPresent());
     }
 
 
     /**
      * Special quad closing for RDF4J.
      */
     private void closeIterable(final Iterable<Quad> iterate) throws Exception {
         if (iterate instanceof AutoCloseable) {
             ((AutoCloseable) iterate).close();
         }
     }
 
     @Test
     public void iterateFilter() throws Exception {
         final List<RDFTerm> friends = new ArrayList<>();
         final IRI alice = factory.createIRI("http://example.com/alice");
         final IRI knows = factory.createIRI("http://xmlns.com/foaf/0.1/knows");
         for (final Quad t : dataset.iterate(null, alice, knows, null)) {
             friends.add(t.getObject());
         }
         assertEquals(1, friends.size());
         assertEquals(bob, friends.get(0));
 
         // .. can we iterate over zero hits?
         final Iterable<Quad> iterate = dataset.iterate(Optional.of(graph2), bob, knows, alice);
         for (final Quad unexpected : iterate) {
             fail("Unexpected quad " + unexpected);
         }
         // closeIterable(iterate);
     }
 
     @Test
     public void contains() throws Exception {
         assertFalse(dataset.contains(null, bob, knows, alice)); // or so he claims..
 
         assertTrue(dataset.contains(Optional.of(graph1), alice, knows, bob));
 
         try (Stream<? extends Quad> stream = dataset.stream()) {
             final Optional<? extends Quad> first = stream.skip(4).findFirst();
             Assume.assumeTrue(first.isPresent());
             final Quad existingQuad = first.get();
             assertTrue(dataset.contains(existingQuad));
         }
 
         final Quad nonExistingQuad = factory.createQuad(graph2, bob, knows, alice);
         assertFalse(dataset.contains(nonExistingQuad));
 
         // An existing quad
         final Quad quad = factory.createQuad(graph1, alice, knows, bob);
         // FIXME: Should not this always be true?
          assertTrue(dataset.contains(quad));
     }
 
     @Test
     public void remove() throws Exception {
         final long fullSize = dataset.size();
         dataset.remove(Optional.of(graph1), alice, knows, bob);
         final long shrunkSize = dataset.size();
         assertEquals(1, fullSize - shrunkSize);
 
         dataset.remove(Optional.of(graph1), alice, knows, bob);
         assertEquals(shrunkSize, dataset.size()); // unchanged
 
         dataset.add(graph1, alice, knows, bob);
         dataset.add(graph2, alice, knows, bob);
         dataset.add(graph2, alice, knows, bob);
         // Undetermined size at this point -- but at least it
         // should be bigger
         assertTrue(dataset.size() > shrunkSize);
 
         // and after a single remove they should all be gone
         dataset.remove(null, alice, knows, bob);
         assertEquals(shrunkSize, dataset.size());
 
         Quad otherQuad;
         try (Stream<? extends Quad> stream = dataset.stream()) {
             final Optional<? extends Quad> anyQuad = stream.findAny();
             Assume.assumeTrue(anyQuad.isPresent());
             otherQuad = anyQuad.get();
         }
 
         dataset.remove(otherQuad);
         assertEquals(shrunkSize - 1, dataset.size());
         dataset.remove(otherQuad);
         assertEquals(shrunkSize - 1, dataset.size()); // no change
 
         // for some reason in rdf4j this causes duplicates!
         dataset.add(otherQuad);
         // dataset.stream().forEach(System.out::println);
         // should have increased
         assertTrue(dataset.size() >= shrunkSize);
     }
 
     @Test
     public void clear() throws Exception {
         dataset.clear();
         assertFalse(dataset.contains(null, alice, knows, bob));
         assertEquals(0, dataset.size());
         dataset.clear(); // no-op
         assertEquals(0, dataset.size());
         assertFalse(dataset.contains(null, null, null, null)); // nothing here
     }
 
     @Test
     public void getQuads() throws Exception {
         long quadCount;
         try (Stream<? extends Quad> stream = dataset.stream()) {
             quadCount = stream.count();
         }
         assertTrue(quadCount > 0);
 
         try (Stream<? extends Quad> stream = dataset.stream()) {
             assertTrue(stream.allMatch(t -> dataset.contains(t)));
         }
 
         // Check exact count
         Assume.assumeNotNull(bnode1, bnode2, aliceName, bobName, secretClubName, companyName, bobNameQuad);
         assertEquals(10, quadCount);
     }
 
     @Test
     public void getQuadsQuery() throws Exception {
 
         try (Stream<? extends Quad> stream = dataset.stream(Optional.of(graph1), alice, null, null)) {
             final long aliceCount = stream.count();
             assertTrue(aliceCount > 0);
             Assume.assumeNotNull(aliceName);
             assertEquals(3, aliceCount);
         }
 
         Assume.assumeNotNull(bnode1, bnode2, bobName, companyName, secretClubName);
         try (Stream<? extends Quad> stream = dataset.stream(null, null, name, null)) {
             assertEquals(4, stream.count());
         }
         Assume.assumeNotNull(bnode1);
         try (Stream<? extends Quad> stream = dataset.stream(null, null, member, null)) {
             assertEquals(3, stream.count());
         }
     }
 
     @Test
     public void addBlankNodesFromMultipleDatasets() throws Exception {
         // Create two separate Dataset instances
         try (final Dataset g1 = createDataset1();
                 final Dataset g2 = createDataset2();
                 final Dataset g3 = factory.createDataset()) {
 
             addAllQuads(g1, g3);
             addAllQuads(g2, g3);
 
             // Let's make a map to find all those blank nodes after insertion
             // (The Dataset implementation is not currently required to
             // keep supporting those BlankNodes with contains() - see
             // COMMONSRDF-15)
 
             final Map<String, BlankNodeOrIRI> whoIsWho = new ConcurrentHashMap<>();
             // ConcurrentHashMap as we will try parallel forEach below,
             // which should not give inconsistent results (it does with a
             // HashMap!)
 
             // look up BlankNodes by name
             final IRI name = factory.createIRI("http://xmlns.com/foaf/0.1/name");
             try (Stream<? extends Quad> stream = g3.stream(null, null, name, null)) {
                 stream.parallel().forEach(t -> whoIsWho.put(t.getObject().ntriplesString(), t.getSubject()));
             }
 
             assertEquals(4, whoIsWho.size());
             // and contains 4 unique values
             assertEquals(4, new HashSet<>(whoIsWho.values()).size());
 
             final BlankNodeOrIRI b1Alice = whoIsWho.get("\"Alice\"");
             assertNotNull(b1Alice);
             final BlankNodeOrIRI b2Bob = whoIsWho.get("\"Bob\"");
             assertNotNull(b2Bob);
             final BlankNodeOrIRI b1Charlie = whoIsWho.get("\"Charlie\"");
             assertNotNull(b1Charlie);
             final BlankNodeOrIRI b2Dave = whoIsWho.get("\"Dave\"");
             assertNotNull(b2Dave);
 
             // All blank nodes should differ
             notEquals(b1Alice, b2Bob);
             notEquals(b1Alice, b1Charlie);
             notEquals(b1Alice, b2Dave);
             notEquals(b2Bob, b1Charlie);
             notEquals(b2Bob, b2Dave);
             notEquals(b1Charlie, b2Dave);
 
             // And we should be able to query with them again
             // as we got them back from g3
             final IRI hasChild = factory.createIRI("http://example.com/hasChild");
             // FIXME: Check graph2 BlankNode in these ..?
             assertTrue(g3.contains(null, b1Alice, hasChild, b2Bob));
             assertTrue(g3.contains(null, b2Dave, hasChild, b1Charlie));
             // But not
             assertFalse(g3.contains(null, b1Alice, hasChild, b1Alice));
             assertFalse(g3.contains(null, b1Alice, hasChild, b1Charlie));
             assertFalse(g3.contains(null, b1Alice, hasChild, b2Dave));
             // nor
             assertFalse(g3.contains(null, b2Dave, hasChild, b1Alice));
             assertFalse(g3.contains(null, b2Dave, hasChild, b1Alice));
 
             // and these don't have any children (as far as we know)
             assertFalse(g3.contains(null, b2Bob, hasChild, null));
             assertFalse(g3.contains(null, b1Charlie, hasChild, null));
         }
     }
 
     private void notEquals(final BlankNodeOrIRI node1, final BlankNodeOrIRI node2) {
         assertFalse(node1.equals(node2));
         // in which case we should be able to assume
         // (as they are in the same dataset)
         assertFalse(node1.ntriplesString().equals(node2.ntriplesString()));
     }
 
     /**
      * Add all quads from the source to the target.
      * <p>
      * The quads may be copied in any order. No special conversion or
      * adaptation of {@link BlankNode}s are performed.
      *
      * @param source
      *            Source Dataset to copy quads from
      * @param target
      *            Target Dataset where quads will be added
      */
     private void addAllQuads(final Dataset source, final Dataset target) {
 
         // unordered() as we don't need to preserve quad order
         // sequential() as we don't (currently) require target Dataset to be
         // thread-safe
 
         try (Stream<? extends Quad> stream = source.stream()) {
             stream.unordered().sequential().forEach(t -> target.add(t));
         }
     }
 
     /**
      * Make a new dataset with two BlankNodes - each with a different
      * uniqueReference
      */
     private Dataset createDataset1() {
         final RDF factory1 = createFactory();
 
         final IRI name = factory1.createIRI("http://xmlns.com/foaf/0.1/name");
         final Dataset g1 = factory1.createDataset();
         final BlankNode b1 = createOwnBlankNode("b1", "0240eaaa-d33e-4fc0-a4f1-169d6ced3680");
         g1.add(b1, b1, name, factory1.createLiteral("Alice"));
 
         final BlankNode b2 = createOwnBlankNode("b2", "9de7db45-0ce7-4b0f-a1ce-c9680ffcfd9f");
         g1.add(b2, b2, name, factory1.createLiteral("Bob"));
 
         final IRI hasChild = factory1.createIRI("http://example.com/hasChild");
         g1.add(null, b1, hasChild, b2);
 
         return g1;
     }
 
     /**
      * Create a different implementation of BlankNode to be tested with
      * dataset.add(a,b,c); (the implementation may or may not then choose to
      * translate such to its own instances)
      *
      * @param name
      * @return
      */
     private BlankNode createOwnBlankNode(final String name, final String uuid) {
         return new BlankNode() {
             @Override
             public String ntriplesString() {
                 return "_: " + name;
             }
 
             @Override
             public String uniqueReference() {
                 return uuid;
             }
 
             @Override
             public int hashCode() {
                 return uuid.hashCode();
             }
 
             @Override
             public boolean equals(final Object obj) {
                 if (!(obj instanceof BlankNode)) {
                     return false;
                 }
                 final BlankNode other = (BlankNode) obj;
                 return uuid.equals(other.uniqueReference());
             }
         };
     }
 
     private Dataset createDataset2() {
         final RDF factory2 = createFactory();
         final IRI name = factory2.createIRI("http://xmlns.com/foaf/0.1/name");
 
         final Dataset g2 = factory2.createDataset();
 
         final BlankNode b1 = createOwnBlankNode("b1", "bc8d3e45-a08f-421d-85b3-c25b373abf87");
         g2.add(b1, b1, name, factory2.createLiteral("Charlie"));
 
         final BlankNode b2 = createOwnBlankNode("b2", "2209097a-5078-4b03-801a-6a2d2f50d739");
         g2.add(b2, b2, name, factory2.createLiteral("Dave"));
 
         final IRI hasChild = factory2.createIRI("http://example.com/hasChild");
         // NOTE: Opposite direction of loadDataset1
         g2.add(b2, b2, hasChild, b1);
         return g2;
     }
 
     /**
      * Ensure {@link Dataset#getGraphNames()} contains our two graphs.
      *
      * @throws Exception
      *             If test fails
      */
     @Test
     public void getGraphNames() throws Exception {
         final Set<BlankNodeOrIRI> names = dataset.getGraphNames().collect(Collectors.toSet());
         assertTrue("Can't find graph name " + graph1, names.contains(graph1));
         assertTrue("Found no quads in graph1", dataset.contains(Optional.of(graph1), null, null, null));
 
         final Optional<BlankNodeOrIRI> graphName2 = dataset.getGraphNames().filter(BlankNode.class::isInstance).findAny();
         assertTrue("Could not find graph2-like BlankNode", graphName2.isPresent());
         assertTrue("Found no quads in graph2", dataset.contains(graphName2, null, null, null));
 
         // Some implementations like Virtuoso might have additional internal graphs,
         // so we can't assume this:
         //assertEquals(2, names.size());
     }
 
     @Test
     public void getGraph() throws Exception {
         try (final Graph defaultGraph = dataset.getGraph()) {
             // TODO: Can we assume the default graph was empty before our new triples?
             assertEquals(2, defaultGraph.size());
             assertTrue(defaultGraph.contains(alice, isPrimaryTopicOf, graph1));
             // NOTE: graph2 is a BlankNode
             assertTrue(defaultGraph.contains(bob, isPrimaryTopicOf, null));
         }
     }
 
 
     @Test
     public void getGraphNull() throws Exception {
         // Default graph should be present
         try (final Graph defaultGraph = dataset.getGraph(null).get()) {
             // TODO: Can we assume the default graph was empty before our new triples?
             assertEquals(2, defaultGraph.size());
             assertTrue(defaultGraph.contains(alice, isPrimaryTopicOf, graph1));
             // NOTE: wildcard as graph2 is a (potentially mapped) BlankNode
             assertTrue(defaultGraph.contains(bob, isPrimaryTopicOf, null));
         }
     }
 
 
     @Test
     public void getGraph1() throws Exception {
         // graph1 should be present
         try (final Graph g1 = dataset.getGraph(graph1).get()) {
             assertEquals(4, g1.size());
 
             assertTrue(g1.contains(alice, name, aliceName));
             assertTrue(g1.contains(alice, knows, bob));
             assertTrue(g1.contains(alice, member, null));
             assertTrue(g1.contains(null, name, secretClubName));
         }
     }
 
     @Test
     public void getGraph2() throws Exception {
         // graph2 should be present, even if is named by a BlankNode
         // We'll look up the potentially mapped graph2 blanknode
         final BlankNodeOrIRI graph2Name = (BlankNodeOrIRI) dataset.stream(Optional.empty(), bob, isPrimaryTopicOf, null)
                 .map(Quad::getObject).findAny().get();
 
         try (final Graph g2 = dataset.getGraph(graph2Name).get()) {
             assertEquals(4, g2.size());
             final Triple bobNameTriple = bobNameQuad.asTriple();
             assertTrue(g2.contains(bobNameTriple));
             assertTrue(g2.contains(bob, member, bnode1));
             assertTrue(g2.contains(bob, member, bnode2));
             assertFalse(g2.contains(bnode1, name, secretClubName));
             assertTrue(g2.contains(bnode2, name, companyName));
         }
     }
 
     @Test
     public void containsLanguageTagsCaseInsensitive() {
         // COMMONSRDF-51: Ensure we can add/contains/remove with any casing
         // of literal language tag
         final Literal lower = factory.createLiteral("Hello there", "en-gb");
         final Literal upper = factory.createLiteral("Hello there", "EN-GB");
         final Literal mixed = factory.createLiteral("Hello there", "en-GB");
 
         final IRI example1 = factory.createIRI("http://example.com/s1");
         final IRI greeting = factory.createIRI("http://example.com/greeting");
 
 
         dataset.add(null, example1, greeting, upper);
 
         // any kind of Triple should match
         assertTrue(dataset.contains(factory.createQuad(null, example1, greeting, upper)));
         assertTrue(dataset.contains(factory.createQuad(null, example1, greeting, lower)));
         assertTrue(dataset.contains(factory.createQuad(null, example1, greeting, mixed)));
 
         // or as patterns
         assertTrue(dataset.contains(null, null, null, upper));
         assertTrue(dataset.contains(null, null, null, lower));
         assertTrue(dataset.contains(null, null, null, mixed));
     }
 
     @Test
     public void containsLanguageTagsCaseInsensitiveTurkish() {
         // COMMONSRDF-51: Special test for Turkish issue where
         // "i".toLowerCase() != "i"
         // See also:
         // https://garygregory.wordpress.com/2015/11/03/java-lowercase-conversion-turkey/
 
         // This is similar to the test in AbstractRDFTest, but on a graph
         final Locale defaultLocale = Locale.getDefault();
         try {
             Locale.setDefault(Locale.ROOT);
             final Literal lowerROOT = factory.createLiteral("moi", "fi");
             final Literal upperROOT = factory.createLiteral("moi", "FI");
             final Literal mixedROOT = factory.createLiteral("moi", "fI");
             final IRI exampleROOT = factory.createIRI("http://example.com/s1");
             final IRI greeting = factory.createIRI("http://example.com/greeting");
             dataset.add(null, exampleROOT, greeting, mixedROOT);
 
             final Locale turkish = Locale.forLanguageTag("TR");
             Locale.setDefault(turkish);
             // If the below assertion fails, then the Turkish
             // locale no longer have this peculiarity that
             // we want to test.
             Assume.assumeFalse("FI".toLowerCase().equals("fi"));
 
             // Below is pretty much the same as in
             // containsLanguageTagsCaseInsensitive()
             final Literal lower = factory.createLiteral("moi", "fi");
             final Literal upper = factory.createLiteral("moi", "FI");
             final Literal mixed = factory.createLiteral("moi", "fI");
 
             final IRI exampleTR = factory.createIRI("http://example.com/s2");
             dataset.add(null, exampleTR, greeting, upper);
             assertTrue(dataset.contains(factory.createQuad(null, exampleTR, greeting, upper)));
             assertTrue(dataset.contains(factory.createQuad(null, exampleTR, greeting, upperROOT)));
             assertTrue(dataset.contains(factory.createQuad(null, exampleTR, greeting, lower)));
             assertTrue(dataset.contains(factory.createQuad(null, exampleTR, greeting, lowerROOT)));
             assertTrue(dataset.contains(factory.createQuad(null, exampleTR, greeting, mixed)));
             assertTrue(dataset.contains(factory.createQuad(null, exampleTR, greeting, mixedROOT)));
             assertTrue(dataset.contains(null, exampleTR, null, upper));
             assertTrue(dataset.contains(null, exampleTR, null, upperROOT));
             assertTrue(dataset.contains(null, exampleTR, null, lower));
             assertTrue(dataset.contains(null, exampleTR, null, lowerROOT));
             assertTrue(dataset.contains(null, exampleTR, null, mixed));
             assertTrue(dataset.contains(null, exampleTR, null, mixedROOT));
 
             // What about the triple we added while in ROOT locale?
             assertTrue(dataset.contains(factory.createQuad(null, exampleROOT, greeting, upper)));
             assertTrue(dataset.contains(factory.createQuad(null, exampleROOT, greeting, lower)));
             assertTrue(dataset.contains(factory.createQuad(null, exampleROOT, greeting, mixed)));
             assertTrue(dataset.contains(null, exampleROOT, null, upper));
             assertTrue(dataset.contains(null, exampleROOT, null, lower));
             assertTrue(dataset.contains(null, exampleROOT, null, mixed));
         } finally {
             Locale.setDefault(defaultLocale);
         }
     }
 
 
     @Test
     public void removeLanguageTagsCaseInsensitive() {
         // COMMONSRDF-51: Ensure we can remove with any casing
         // of literal language tag
         final Literal lower = factory.createLiteral("Howdy", "en-us");
         final Literal upper = factory.createLiteral("Howdy", "EN-US");
         final Literal mixed = factory.createLiteral("Howdy", "en-US");
 
         final IRI example1 = factory.createIRI("http://example.com/s1");
         final IRI greeting = factory.createIRI("http://example.com/greeting");
 
         dataset.add(null, example1, greeting, upper);
 
         // Remove should also honour any case
         dataset.remove(null, example1, null, mixed);
         assertFalse(dataset.contains(null, null, greeting, null));
 
         dataset.add(null, example1, greeting, lower);
         dataset.remove(null, example1, null, upper);
 
         // Check with Triple
         dataset.add(factory.createQuad(null, example1, greeting, mixed));
         dataset.remove(factory.createQuad(null, example1, greeting, upper));
         assertFalse(dataset.contains(null, null, greeting, null));
     }
 
     private static Optional<? extends Quad> closableFindAny(final Stream<? extends Quad> stream) {
         try (Stream<? extends Quad> s = stream) {
             return s.findAny();
         }
     }
 
     @Test
     public void streamLanguageTagsCaseInsensitive() {
         // COMMONSRDF-51: Ensure we can add/contains/remove with any casing
         // of literal language tag
         final Literal lower = factory.createLiteral("Good afternoon", "en-gb");
         final Literal upper = factory.createLiteral("Good afternoon", "EN-GB");
         final Literal mixed = factory.createLiteral("Good afternoon", "en-GB");
 
         final IRI example1 = factory.createIRI("http://example.com/s1");
         final IRI greeting = factory.createIRI("http://example.com/greeting");
 
         dataset.add(null, example1, greeting, upper);
 
         // or as patterns
         assertTrue(closableFindAny(dataset.stream(null, null, null, upper)).isPresent());
         assertTrue(closableFindAny(dataset.stream(null, null, null, lower)).isPresent());
         assertTrue(closableFindAny(dataset.stream(null, null, null, mixed)).isPresent());
 
         // Check the quad returned equal a new quad
         final Quad q = closableFindAny(dataset.stream(null, null, null, lower)).get();
         assertEquals(q, factory.createQuad(null, example1, greeting, mixed));
     }
 
     /**
      * An attempt to use the Java 8 streams to look up a more complicated query.
      * <p>
      * FYI, the equivalent SPARQL version (untested):
      *
      * <pre>
      *     SELECT ?orgName WHERE {
      *             ?org foaf:name ?orgName .
      *             ?alice foaf:member ?org .
      *             ?bob foaf:member ?org .
      *             ?alice foaf:knows ?bob .
      *           FILTER NOT EXIST { ?bob foaf:knows ?alice }
      *    }
      * </pre>
      *
      * @throws Exception If test fails
      */
     @Test
     public void whyJavaStreamsMightNotTakeOverFromSparql() throws Exception {
         Assume.assumeNotNull(bnode1, bnode2, secretClubName);
         // Find a secret organizations
         try (Stream<? extends Quad> stream = dataset.stream(null, null, knows, null)) {
             assertEquals("\"The Secret Club\"",
                     // Find One-way "knows"
                     stream.filter(t -> !dataset.contains(null, (BlankNodeOrIRI) t.getObject(), knows, t.getSubject()))
                             .map(knowsQuad -> {
                                 try (Stream<? extends Quad> memberOf = dataset
                                         // and those they know, what are they
                                         // member of?
                                         .stream(null, (BlankNodeOrIRI) knowsQuad.getObject(), member, null)) {
                                     return memberOf
                                             // keep those which first-guy is a
                                             // member of
                                             .filter(memberQuad -> dataset.contains(null, knowsQuad.getSubject(), member,
                                                     // First hit is good enough
                                                     memberQuad.getObject()))
                                             .findFirst().get().getObject();
                                 }
                             })
                             // then look up the name of that org
                             .map(org -> {
                                 try (Stream<? extends Quad> orgName = dataset.stream(null, (BlankNodeOrIRI) org, name,
                                         null)) {
                                     return orgName.findFirst().get().getObject().ntriplesString();
                                 }
                             }).findFirst().get());
         }
     }
 }