Add tests to Math (#423)

* Add prettier config

* test: add test to check for absolute function

* chore: es5 to es6

* test: add test to check mean function

* test: add test for sum of digit

* test: add test for factorial

* test: add test for fibonnaci

* test: add test for find HCF

* test: add test for lcm

* test: add gridget test

* test: add test for mean square error

* test: add test for modular binary exponentiation

* test: add tests for palindrome

* test: add test for pascals triangle

* test: add tests for polynomial

* test: add tests for prime check

* test: add tests for reverse polish notation

* test: add tests for sieve of eratosthenes

* test: add tests for pi estimation monte carlo method

* chore: move tests to test folder

* chore: fix standardjs errors

String/test/CheckPalindrome.test.js

@@ -0,0 +1,16 @@
+import { checkPalindrome } from '../CheckPalindrome'
+
+describe('checkPalindrome', () => {
+  it('expects to return "Palindrome" if the given string is a palindrome', () => {
+    const SUT = checkPalindrome('madam')
+    expect(SUT).toBe('Palindrome')
+  })
+  it('expects to return "Empty string" if the given string is empty', () => {
+    const SUT = checkPalindrome('')
+    expect(SUT).toBe('Empty string')
+  })
+  it('expects to return "Not a string" if the given string is not a string', () => {
+    const SUT = checkPalindrome(123)
+    expect(SUT).toBe('Not a string')
+  })
+})