android/guava-tests/test/com/google/common/collect/TreeTraverserTest.java

/*
 * Copyright (C) 2011 The Guava Authors
 *
 * 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 com.google.common.collect;

import static com.google.common.truth.Truth.assertThat;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.base.Function;
import com.google.common.testing.NullPointerTester;
import java.util.Arrays;
import java.util.List;
import junit.framework.TestCase;

/**
 * Tests for {@code TreeTraverser}.
 *
 * @author Louis Wasserman
 */
@GwtCompatible(emulated = true)
public class TreeTraverserTest extends TestCase {
  private static class Node {
    final char value;

    Node(char value) {
      this.value = value;
    }
  }

  private static final class Tree extends Node {
    final List<Tree> children;

    public Tree(char value, Tree... children) {
      super(value);
      this.children = Arrays.asList(children);
    }
  }

  private static final TreeTraverser<Tree> ADAPTER =
      new TreeTraverser<Tree>() {
        @Override
        public Iterable<Tree> children(Tree node) {
          return node.children;
        }
      };

  private static final TreeTraverser<Tree> ADAPTER_USING_USING =
      TreeTraverser.using(
          new Function<Tree, Iterable<Tree>>() {
            @Override
            public Iterable<Tree> apply(Tree node) {
              return node.children;
            }
          });

  //        h
  //      / | \
  //     /  e  \
  //    d       g
  //   /|\      |
  //  / | \     f
  // a  b  c
  static final Tree a = new Tree('a');
  static final Tree b = new Tree('b');
  static final Tree c = new Tree('c');
  static final Tree d = new Tree('d', a, b, c);
  static final Tree e = new Tree('e');
  static final Tree f = new Tree('f');
  static final Tree g = new Tree('g', f);
  static final Tree h = new Tree('h', d, e, g);

  static String iterationOrder(Iterable<? extends Node> iterable) {
    StringBuilder builder = new StringBuilder();
    for (Node t : iterable) {
      builder.append(t.value);
    }
    return builder.toString();
  }

  public void testPreOrder() {
    assertThat(iterationOrder(ADAPTER.preOrderTraversal(h))).isEqualTo("hdabcegf");
  }

  public void testPostOrder() {
    assertThat(iterationOrder(ADAPTER.postOrderTraversal(h))).isEqualTo("abcdefgh");
  }

  public void testBreadthOrder() {
    assertThat(iterationOrder(ADAPTER.breadthFirstTraversal(h))).isEqualTo("hdegabcf");
  }

  public void testUsing() {
    assertThat(iterationOrder(ADAPTER_USING_USING.preOrderTraversal(h))).isEqualTo("hdabcegf");
  }

  @GwtIncompatible // NullPointerTester
  public void testNulls() {
    NullPointerTester tester = new NullPointerTester();
    tester.testAllPublicInstanceMethods(ADAPTER);
  }
}