Add max word algorithm

String/test/MaxWord.test.js

@@ -0,0 +1,12 @@
+import { maxWord } from '../MaxWord'
+
+describe('Testing the maxWord function', () => {
+  it('Expect throw with non string argument', () => {
+    expect(() => maxWord(10)).toThrow()
+  })
+  it('get the max word', () => {
+    const string = 'ba ba ba ba banana'
+    const mostOccuringWord = maxWord(string)
+    expect(mostOccuringWord).toBe('ba')
+  })
+})