import org.junit.Assert;

import org.junit.Test;

import java.util.Arrays;

import java.util.Collections;

public class BinaryTreeLevelOrderTraversalTest {

@Test

public void testLevelOrder() {

BinaryTreeLevelOrderTraversal b = new BinaryTreeLevelOrderTraversal();

Assert.assertTrue(b.levelOrder(null).isEmpty());

BinaryTreeLevelOrderTraversal.TreeNode node0 = new BinaryTreeLevelOrderTraversal.TreeNode(1);

Assert.assertEquals(b.levelOrder(node0), Collections.singletonList(Collections.singletonList(1)));

BinaryTreeLevelOrderTraversal.TreeNode node1 = new BinaryTreeLevelOrderTraversal.TreeNode(3);

node1.left = new BinaryTreeLevelOrderTraversal.TreeNode(9);

node1.right = new BinaryTreeLevelOrderTraversal.TreeNode(20);

node1.right.left = new BinaryTreeLevelOrderTraversal.TreeNode(15);

node1.right.right = new BinaryTreeLevelOrderTraversal.TreeNode(7);

Assert.assertEquals(b.levelOrder(node1), Arrays.asList(Collections.singletonList(3), Arrays.asList(9, 20), Arrays.asList(15, 7)));

}

}