fix: throw error and add tests for ReverseNumber (#1608)

Maths/ReverseNumber.js

@@ -10,7 +10,7 @@
 const ReverseNumber = (number) => {
   // firstly, check that input is a number or not.
   if (typeof number !== 'number') {
-    return new TypeError('Argument is not a number.')
+    throw new TypeError('Argument is not a number.')
   }
   // A variable for storing the reversed number.
   let reverseNumber = 0

Maths/test/ReverseNumber.test.js

@@ -0,0 +1,16 @@
+import { ReverseNumber } from '../ReverseNumber'
+
+describe('ReverseNumber', () => {
+  it.each([
+    [0, 0],
+    [10, 1],
+    [123, 321],
+    [100001, 100001]
+  ])('check with %j', (input, expected) => {
+    expect(expected).toEqual(ReverseNumber(input))
+  })
+
+  it('should throw when input is not a number', () => {
+    expect(() => ReverseNumber('100')).toThrowError()
+  })
+})