BinaryTreeLevelOrderTraversalTest.java

import org.example.helpers.TreeNode;
import org.example.problems.binary_tree_level_order_traversal.Solution;
import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.Arguments;
import org.junit.jupiter.params.provider.MethodSource;

import java.util.ArrayList;
import java.util.stream.Stream;

public class BinaryTreeLevelOrderTraversalTest {
 private static Stream<Arguments> provideCases() {
 return Stream.of(
 Arguments.of(
 new TreeNode(
 3,
 new TreeNode(9),
 new TreeNode(20, new TreeNode(15), new TreeNode(7))),
 new int[][]{{3},{9,20},{15,7}}
 ),
 Arguments.of(
 new TreeNode(1),
 new int[][]{{1}}
 ),
 Arguments.of(
 null,
 new int[][]{}
 )
 );
 }

 @ParameterizedTest
 @MethodSource("provideCases")
 public void test(TreeNode node, int[][] expected) {
 Solution s = new Solution();
 ArrayList<ArrayList<Integer>> expectedList = new ArrayList<>();
 for (int[] ar: expected) {
 ArrayList<Integer> sublist = new ArrayList<>();
 for (int i: ar) {
 sublist.add(i);
 }
 expectedList.add(sublist);
 }
 Assertions.assertEquals(expectedList, s.levelOrder(node));
 }
}