code: ///////////////////////////////////////////////////////////////////////////
  //                   __                _      _   ________               //
  //                  / /   ____  ____ _(_)____/ | / / ____/               //
  //                 / /   / __ \/ __ `/ / ___/  |/ / / __                 //
  //                / /___/ /_/ / /_/ / / /__/ /|  / /_/ /                 //
  //               /_____/\____/\__, /_/\___/_/ |_/\____/                  //
  //                           /____/                                      //
  //                                                                       //
  //               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.solvers.datastructures;
  
  import static org.assertj.core.api.Assertions.assertThat;
  
  import org.junit.jupiter.api.Test;
  import org.logicng.solvers.sat.MiniCard;
  import org.logicng.solvers.sat.MiniSatStyleSolver;
  
  /**
   * Unit tests for the class {@link LNGHeap}.
   * @version 2.0.0
   * @since 1.1
   */
  public class LNGHeapTest {
  
      @Test
      public void test() {
          final MiniSatStyleSolver solver = new MiniCard();
          solver.newVar(true, true);
          solver.newVar(true, true);
          solver.newVar(true, true);
          final LNGHeap heap = new LNGHeap(solver);
          assertThat(heap.empty()).isTrue();
          heap.insert(1);
          heap.insert(2);
          heap.insert(0);
          assertThat(heap.get(0)).isEqualTo(1);
          assertThat(heap.toString()).isEqualTo("LNGHeap{[1, 2], [2, 0], [0, 1]}");
          assertThat(heap.size()).isEqualTo(3);
          heap.clear();
          assertThat(heap.empty()).isTrue();
      }
  }
  