Added HammingDistance.js and HammingDistance.test.js in String directory

String/test/HammingDistance.test.js

@@ -0,0 +1,21 @@
+import { hammingDistance } from '../HammingDistance'
+
+test('should throw an error when trying to compare the strings of different length', () => {
+  const compareStringsOfDifferentLength = () => {
+    hammingDistance('abc', 'abcd')
+  }
+
+  expect(compareStringsOfDifferentLength).toThrowError()
+})
+
+test('should calculate difference between two strings', () => {
+  expect(hammingDistance('a', 'a')).toBe(0)
+})
+
+test('should calculate difference between two strings', () => {
+  expect(hammingDistance('abc', 'add')).toBe(2)
+})
+
+test('should calculate difference between two strings', () => {
+  expect(hammingDistance('1011101', '1001001')).toBe(2)
+})