Add Test for Binary Tree Preorder Traversal

Author: theIYD

src/_DataStructures_/Trees/BinaryTree/btree-traversals.test.js

@@ -0,0 +1,17 @@
+const BinaryTree = require("./index");
+
+describe("Binary Tree Preorder Traversal", () => {
+  let btree;
+  let preOrderTraversal;
+
+  describe("Creates BTree", () => {
+    btree = new BinaryTree([1, 2, 3, 4, 5, 6]);
+  });
+
+  describe("BTree Traversals", () => {
+    it("should compute the Preorder traversal for the above created binary tree", () => {
+      preOrderTraversal = btree.preOrder();
+      expect(preOrderTraversal).toEqual([1, 2, 4, 5, 3, 6]);
+    });
+  });
+});