code: ///////////////////////////////////////////////////////////////////////////
  //                   __                _      _   ________               //
  //                  / /   ____  ____ _(_)____/ | / / ____/               //
  //                 / /   / __ \/ __ `/ / ___/  |/ / / __                 //
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  //               /_____/\____/\__, /_/\___/_/ |_/\____/                  //
  //                           /____/                                      //
  //                                                                       //
  //               The Next Generation Logic Library                       //
  //                                                                       //
  ///////////////////////////////////////////////////////////////////////////
  //                                                                       //
  //  Copyright 2015-20xx Christoph Zengler                                //
  //                                                                       //
  //  Licensed 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.logicng.datastructures.ubtrees;
  
  import static org.assertj.core.api.Assertions.assertThat;
  
  import org.junit.jupiter.api.Test;
  
  import java.util.Arrays;
  import java.util.SortedSet;
  import java.util.TreeSet;
  
  /**
   * Unit tests for {@link UBTree}.
   * @version 2.0.0
   * @since 1.5.0
   */
  public class UBTreeTest {
  
      @Test
      public void testEmptySet() {
          final UBTree<String> tree = new UBTree<>();
          tree.addSet(new TreeSet<>());
          assertThat(tree.rootNodes()).isEmpty();
      }
  
      @Test
      public void testSingleSet() {
          final UBTree<String> tree = new UBTree<>();
          tree.addSet(set("A", "B", "C"));
          assertThat(tree.rootNodes()).hasSize(1);
          assertThat(tree.rootNodes().keySet()).containsExactly("A");
          assertThat(tree.rootNodes().get("A").children()).hasSize(1);
          assertThat(tree.rootNodes().get("A").isEndOfPath()).isFalse();
          assertThat(tree.rootNodes().get("A").children().keySet()).containsExactly("B");
          assertThat(tree.rootNodes().get("A").children().get("B").children()).hasSize(1);
          assertThat(tree.rootNodes().get("A").children().get("B").isEndOfPath()).isFalse();
          assertThat(tree.rootNodes().get("A").children().get("B").children().keySet()).containsExactly("C");
          assertThat(tree.rootNodes().get("A").children().get("B").children().get("C").isEndOfPath()).isTrue();
          assertThat(tree.rootNodes().get("A").children().get("B").children().get("C").set()).isEqualTo(set("A", "B", "C"));
          assertThat(tree.rootNodes().get("A").children().get("B").children().get("C").children()).isEmpty();
      }
  
      @Test
      public void testExampleFromPaper() {
          final UBTree<String> tree = new UBTree<>();
          tree.addSet(set("e0", "e1", "e2", "e3"));
          tree.addSet(set("e0", "e1", "e3"));
          tree.addSet(set("e0", "e1", "e2"));
          tree.addSet(set("e2", "e3"));
          assertThat(tree.rootNodes()).hasSize(2);
          assertThat(tree.rootNodes().keySet()).containsExactly("e0", "e2");
  
          // root nodes
          final UBNode<String> e0 = tree.rootNodes().get("e0");
          final UBNode<String> e2 = tree.rootNodes().get("e2");
          assertThat(e0.isEndOfPath()).isFalse();
          assertThat(e0.children().keySet()).containsExactly("e1");
          assertThat(e2.isEndOfPath()).isFalse();
          assertThat(e2.children().keySet()).containsExactly("e3");
  
          // first level
          final UBNode<String> e0e1 = e0.children().get("e1");
          final UBNode<String> e2e3 = e2.children().get("e3");
          assertThat(e0e1.isEndOfPath()).isFalse();
          assertThat(e0e1.children().keySet()).containsExactly("e2", "e3");
          assertThat(e2e3.isEndOfPath()).isTrue();
          assertThat(e2e3.set()).isEqualTo(set("e2", "e3"));
          assertThat(e2e3.children().keySet()).isEmpty();
  
          // second level
          final UBNode<String> e0e1e2 = e0e1.children().get("e2");
          assertThat(e0e1e2.isEndOfPath()).isTrue();
          assertThat(e0e1e2.set()).isEqualTo(set("e0", "e1", "e2"));
          assertThat(e0e1e2.children().keySet()).containsExactly("e3");
          final UBNode<String> e0e1e3 = e0e1.children().get("e3");
          assertThat(e0e1e3.isEndOfPath()).isTrue();
          assertThat(e0e1e3.set()).isEqualTo(set("e0", "e1", "e3"));
          assertThat(e0e1e3.children().keySet()).isEmpty();
  
          //third level
          final UBNode<String> e0e1e2e3 = e0e1e2.children().get("e3");
          assertThat(e0e1e2e3.isEndOfPath()).isTrue();
          assertThat(e0e1e2e3.set()).isEqualTo(set("e0", "e1", "e2", "e3"));
          assertThat(e0e1e2e3.children().keySet()).isEmpty();
      }
  
      @Test
      public void testContainsSubset() {
          final UBTree<String> tree = new UBTree<>();
          final SortedSet<String> e0123 = set("e0", "e1", "e2", "e3");
          final SortedSet<String> e013 = set("e0", "e1", "e3");
          final SortedSet<String> e012 = set("e0", "e1", "e2");
          final SortedSet<String> e23 = set("e2", "e3");
          tree.addSet(e0123);
          tree.addSet(e013);
          tree.addSet(e012);
          tree.addSet(e23);
          assertThat(tree.firstSubset(set("e0"))).isNull();
          assertThat(tree.firstSubset(set("e1"))).isNull();
          assertThat(tree.firstSubset(set("e2"))).isNull();
          assertThat(tree.firstSubset(set("e3"))).isNull();
          assertThat(tree.firstSubset(set("e0", "e1"))).isNull();
          assertThat(tree.firstSubset(set("e0", "e2"))).isNull();
          assertThat(tree.firstSubset(set("e0", "e3"))).isNull();
          assertThat(tree.firstSubset(set("e1", "e2"))).isNull();
          assertThat(tree.firstSubset(set("e1", "e3"))).isNull();
          assertThat(tree.firstSubset(set("e2", "e3"))).isEqualTo(e23);
          assertThat(tree.firstSubset(set("e0", "e1", "e2"))).isEqualTo(e012);
          assertThat(tree.firstSubset(set("e0", "e1", "e3"))).isEqualTo(e013);
          assertThat(tree.firstSubset(set("e0", "e2", "e3"))).isEqualTo(e23);
          assertThat(tree.firstSubset(set("e1", "e2", "e3"))).isEqualTo(e23);
          assertThat(tree.firstSubset(set("e0", "e1", "e2", "e3"))).isIn(e0123, e013, e012, e23);
          assertThat(tree.firstSubset(set("e0", "e4"))).isNull();
          assertThat(tree.firstSubset(set("e1", "e4"))).isNull();
          assertThat(tree.firstSubset(set("e2", "e4"))).isNull();
          assertThat(tree.firstSubset(set("e3", "e4"))).isNull();
          assertThat(tree.firstSubset(set("e0", "e1", "e4"))).isNull();
          assertThat(tree.firstSubset(set("e0", "e2", "e4"))).isNull();
          assertThat(tree.firstSubset(set("e0", "e3", "e4"))).isNull();
          assertThat(tree.firstSubset(set("e1", "e2", "e4"))).isNull();
          assertThat(tree.firstSubset(set("e1", "e3", "e4"))).isNull();
          assertThat(tree.firstSubset(set("e2", "e3", "e4"))).isEqualTo(e23);
          assertThat(tree.firstSubset(set("e0", "e1", "e2", "e4"))).isEqualTo(e012);
          assertThat(tree.firstSubset(set("e0", "e1", "e3", "e4"))).isEqualTo(e013);
          assertThat(tree.firstSubset(set("e0", "e2", "e3", "e4"))).isEqualTo(e23);
          assertThat(tree.firstSubset(set("e1", "e2", "e3", "e4"))).isEqualTo(e23);
          assertThat(tree.firstSubset(set("e0", "e1", "e2", "e3", "e4"))).isIn(e0123, e013, e012, e23);
      }
  
      @Test
      public void testAllSubsets() {
          final UBTree<String> tree = new UBTree<>();
          final SortedSet<String> e0123 = set("e0", "e1", "e2", "e3");
          final SortedSet<String> e013 = set("e0", "e1", "e3");
          final SortedSet<String> e012 = set("e0", "e1", "e2");
          final SortedSet<String> e23 = set("e2", "e3");
          tree.addSet(e0123);
          tree.addSet(e013);
          tree.addSet(e012);
          tree.addSet(e23);
          assertThat(tree.allSubsets(set("e0"))).isEmpty();
          assertThat(tree.allSubsets(set("e1"))).isEmpty();
          assertThat(tree.allSubsets(set("e2"))).isEmpty();
          assertThat(tree.allSubsets(set("e3"))).isEmpty();
          assertThat(tree.allSubsets(set("e0", "e1"))).isEmpty();
          assertThat(tree.allSubsets(set("e0", "e2"))).isEmpty();
          assertThat(tree.allSubsets(set("e0", "e3"))).isEmpty();
          assertThat(tree.allSubsets(set("e1", "e2"))).isEmpty();
          assertThat(tree.allSubsets(set("e1", "e3"))).isEmpty();
          assertThat(tree.allSubsets(set("e2", "e3"))).containsExactlyInAnyOrder(e23);
          assertThat(tree.allSubsets(set("e0", "e1", "e2"))).containsExactlyInAnyOrder(e012);
          assertThat(tree.allSubsets(set("e0", "e1", "e3"))).containsExactlyInAnyOrder(e013);
          assertThat(tree.allSubsets(set("e0", "e2", "e3"))).containsExactlyInAnyOrder(e23);
          assertThat(tree.allSubsets(set("e1", "e2", "e3"))).containsExactlyInAnyOrder(e23);
          assertThat(tree.allSubsets(set("e0", "e1", "e2", "e3"))).containsExactlyInAnyOrder(e0123, e013, e012, e23);
          assertThat(tree.allSubsets(set("e0", "e4"))).isEmpty();
          assertThat(tree.allSubsets(set("e1", "e4"))).isEmpty();
          assertThat(tree.allSubsets(set("e2", "e4"))).isEmpty();
          assertThat(tree.allSubsets(set("e3", "e4"))).isEmpty();
          assertThat(tree.allSubsets(set("e0", "e1", "e4"))).isEmpty();
          assertThat(tree.allSubsets(set("e0", "e2", "e4"))).isEmpty();
          assertThat(tree.allSubsets(set("e0", "e3", "e4"))).isEmpty();
          assertThat(tree.allSubsets(set("e1", "e2", "e4"))).isEmpty();
          assertThat(tree.allSubsets(set("e1", "e3", "e4"))).isEmpty();
          assertThat(tree.allSubsets(set("e2", "e3", "e4"))).containsExactlyInAnyOrder(e23);
          assertThat(tree.allSubsets(set("e0", "e1", "e2", "e4"))).containsExactlyInAnyOrder(e012);
          assertThat(tree.allSubsets(set("e0", "e1", "e3", "e4"))).containsExactlyInAnyOrder(e013);
          assertThat(tree.allSubsets(set("e0", "e2", "e3", "e4"))).containsExactlyInAnyOrder(e23);
          assertThat(tree.allSubsets(set("e1", "e2", "e3", "e4"))).containsExactlyInAnyOrder(e23);
          assertThat(tree.allSubsets(set("e0", "e1", "e2", "e3", "e4"))).containsExactlyInAnyOrder(e0123, e013, e012, e23);
      }
  
      @Test
      public void testAllSupersets() {
          final UBTree<String> tree = new UBTree<>();
          final SortedSet<String> e0123 = set("e0", "e1", "e2", "e3");
          final SortedSet<String> e013 = set("e0", "e1", "e3");
          final SortedSet<String> e012 = set("e0", "e1", "e2");
          final SortedSet<String> e23 = set("e2", "e3");
          tree.addSet(e0123);
          tree.addSet(e013);
          tree.addSet(e012);
          tree.addSet(e23);
          assertThat(tree.allSupersets(set("e4"))).isEmpty();
          assertThat(tree.allSupersets(set("e0"))).containsExactlyInAnyOrder(e0123, e012, e013);
          assertThat(tree.allSupersets(set("e1"))).containsExactlyInAnyOrder(e0123, e012, e013);
          assertThat(tree.allSupersets(set("e2"))).containsExactlyInAnyOrder(e0123, e012, e23);
          assertThat(tree.allSupersets(set("e3"))).containsExactlyInAnyOrder(e0123, e013, e23);
          assertThat(tree.allSupersets(set("e0", "e1"))).containsExactlyInAnyOrder(e0123, e012, e013);
          assertThat(tree.allSupersets(set("e0", "e2"))).containsExactlyInAnyOrder(e0123, e012);
          assertThat(tree.allSupersets(set("e0", "e3"))).containsExactlyInAnyOrder(e0123, e013);
          assertThat(tree.allSupersets(set("e1", "e2"))).containsExactlyInAnyOrder(e0123, e012);
          assertThat(tree.allSupersets(set("e1", "e3"))).containsExactlyInAnyOrder(e0123, e013);
          assertThat(tree.allSupersets(set("e2", "e3"))).containsExactlyInAnyOrder(e0123, e23);
          assertThat(tree.allSupersets(set("e0", "e1", "e2"))).containsExactlyInAnyOrder(e0123, e012);
          assertThat(tree.allSupersets(set("e0", "e2", "e3"))).containsExactlyInAnyOrder(e0123);
          assertThat(tree.allSupersets(set("e0", "e1", "e2", "e3"))).containsExactlyInAnyOrder(e0123);
          assertThat(tree.allSupersets(set("e0", "e4"))).isEmpty();
          assertThat(tree.allSupersets(set("e1", "e4"))).isEmpty();
          assertThat(tree.allSupersets(set("e2", "e4"))).isEmpty();
          assertThat(tree.allSupersets(set("e3", "e4"))).isEmpty();
          assertThat(tree.allSupersets(set("e0", "e1", "e4"))).isEmpty();
          assertThat(tree.allSupersets(set("e0", "e2", "e4"))).isEmpty();
          assertThat(tree.allSupersets(set("e0", "e3", "e4"))).isEmpty();
          assertThat(tree.allSupersets(set("e1", "e2", "e4"))).isEmpty();
          assertThat(tree.allSupersets(set("e1", "e3", "e4"))).isEmpty();
          assertThat(tree.allSupersets(set("e2", "e3", "e4"))).isEmpty();
          assertThat(tree.allSupersets(set("e0", "e1", "e2", "e4"))).isEmpty();
          assertThat(tree.allSupersets(set("e0", "e1", "e3", "e4"))).isEmpty();
          assertThat(tree.allSupersets(set("e0", "e2", "e3", "e4"))).isEmpty();
          assertThat(tree.allSupersets(set("e1", "e2", "e3", "e4"))).isEmpty();
          assertThat(tree.allSupersets(set("e0", "e1", "e2", "e3", "e4"))).isEmpty();
      }
  
      @Test
      public void testAllSets() {
          final UBTree<String> tree = new UBTree<>();
          final SortedSet<String> e0123 = set("e0", "e1", "e2", "e3");
          final SortedSet<String> e013 = set("e0", "e1", "e3");
          final SortedSet<String> e012 = set("e0", "e1", "e2");
          final SortedSet<String> e23 = set("e2", "e3");
          tree.addSet(e0123);
          assertThat(tree.allSets()).containsExactlyInAnyOrder(e0123);
          tree.addSet(e013);
          assertThat(tree.allSets()).containsExactlyInAnyOrder(e0123, e013);
          tree.addSet(e012);
          assertThat(tree.allSets()).containsExactlyInAnyOrder(e0123, e013, e012);
          tree.addSet(e23);
          assertThat(tree.allSets()).containsExactlyInAnyOrder(e0123, e013, e012, e23);
      }
  
      private SortedSet<String> set(final String... elements) {
          return new TreeSet<>(Arrays.asList(elements));
      }
  }
  