adding is palindrome test

Author: alieldeba

project/js/functionality/isPalindrome.js

@@ -5,6 +5,6 @@
  * @returns {boolean}
  */
 function isPalindrome(word) {
-  return word.toString() == reverseString(word.toString());
+  return !word ? "" : word.toString() == word.toString().split("").reverse().join("");
 }
 module.exports = isPalindrome;

tests/isPalindrome.test.js

@@ -0,0 +1,25 @@
+const isPalindrome = require("../project/js/functionality/isPalindrome.js");
+
+it("always returns a boolean value", function () {
+  expect(typeof isPalindrome("123")).toBe("boolean");
+});
+
+it("returns true if word is palindrome", function () {
+  expect(isPalindrome("mum")).toBe(true);
+});
+
+it("returns false if word is not palindrome", function () {
+  expect(isPalindrome("muom")).toBe(false);
+});
+
+it("returns true if word is palindrome also if the parameter is number", function () {
+  expect(isPalindrome(121)).toBe(true);
+});
+
+it("returns false if word is not palindrome also if the parameter is number", function () {
+  expect(isPalindrome(123)).toBe(false);
+});
+
+it("returns empty string if there is no parameter", function () {
+  expect(isPalindrome()).toBe("");
+});