Add unit test for CeilInBinarySearchTree (fixes #3395) (#3396)

Co-authored-by: Amit Kumar <akumar@indeed.com>

src/test/java/com/thealgorithms/datastructures/trees/CeilInBinarySearchTreeTest.java

@@ -0,0 +1,51 @@
+package com.thealgorithms.datastructures.trees;
+
+import com.thealgorithms.datastructures.trees.BinaryTree.Node;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+public class CeilInBinarySearchTreeTest {
+
+    @Test
+    public void testRootNull() {
+        assertNull(CeilInBinarySearchTree.getCeil(null, 9));
+    }
+
+    @Test
+    public void testKeyPresentRootIsCeil() {
+        final Node root = TreeTestUtils.createTree(new Integer[]{100, 10, 200});
+        assertEquals(100, CeilInBinarySearchTree.getCeil(root, 100).data);
+    }
+
+    @Test
+    public void testKeyPresentLeafIsCeil() {
+        final Node root = TreeTestUtils.createTree(new Integer[]{100, 10, 200});
+        assertEquals(10, CeilInBinarySearchTree.getCeil(root, 10).data);
+    }
+
+    @Test
+    public void testKeyAbsentRootIsCeil() {
+        final Node root = TreeTestUtils.createTree(new Integer[]{100, 10, 200, 5, 50, 150, 300});
+        assertEquals(100, CeilInBinarySearchTree.getCeil(root, 75).data);
+    }
+
+    @Test
+    public void testKeyAbsentLeafIsCeil() {
+        final Node root = TreeTestUtils.createTree(new Integer[]{100, 10, 200, 5, 50, 150, 300});
+        assertEquals(50, CeilInBinarySearchTree.getCeil(root, 40).data);
+    }
+
+    @Test
+    public void testKeyAbsentLeftMostNodeIsCeil() {
+        final Node root = TreeTestUtils.createTree(new Integer[]{100, 10, 200, 5, 50, 150, 300});
+        assertEquals(5, CeilInBinarySearchTree.getCeil(root, 1).data);
+    }
+
+    @Test
+    public void testKeyAbsentCeilIsNull() {
+        final Node root = TreeTestUtils.createTree(new Integer[]{100, 10, 200, 5, 50, 150, 300});
+        assertNull(CeilInBinarySearchTree.getCeil(root, 400));
+    }
+}

src/test/java/com/thealgorithms/datastructures/trees/TreeTestUtils.java

@@ -0,0 +1,44 @@
+package com.thealgorithms.datastructures.trees;
+
+import java.util.LinkedList;
+import java.util.Queue;
+import com.thealgorithms.datastructures.trees.BinaryTree.Node;
+
+public class TreeTestUtils {
+
+    /**
+     * Creates a binary tree with given values
+     *
+     * @param values: Level order representation of tree
+     * @return Root of a binary tree
+     */
+    public static Node createTree(final Integer[] values) {
+        if (values == null || values.length == 0 || values[0] == null) {
+            throw new IllegalArgumentException("Values array should not be empty or null.");
+        }
+        final Node root = new Node(values[0]);
+        final Queue<Node> queue = new LinkedList<>();
+        queue.add(root);
+        int end = 1;
+        while (end < values.length) {
+            final Node node = queue.remove();
+            if (values[end] == null) {
+                node.left = null;
+            } else {
+                node.left = new Node(values[end]);
+                queue.add(node.left);
+            }
+            end++;
+            if (end < values.length) {
+                if (values[end] == null) {
+                    node.right = null;
+                } else {
+                    node.right = new Node(values[end]);
+                    queue.add(node.right);
+                }
+            }
+            end++;
+        }
+        return root;
+    }
+}