diff --git a/String/CountVowels.js b/String/CountVowels.js
index d9dc42368a..face0a12b9 100644
--- a/String/CountVowels.js
+++ b/String/CountVowels.js
@@ -1,21 +1,19 @@
 /**
  * @function countVowels
- * @description Given a string of words or phrases, count the number of vowels.
- * @param {String} str - The input string
- * @return {Number} - The number of vowels
- * @example countVowels("ABCDE") => 2
- * @example countVowels("Hello") => 2
+ * @description Counts the number of vowels (a, e, i, o, u) in a string,
+ *   ignoring case.
+ * @param {string} str - The input string
+ * @returns {number} - The number of vowels in the string
+ * @see https://en.wikipedia.org/wiki/Vowel
+ * @example countVowels("hello") => 2
+ * @example countVowels("rhythm") => 0
+ * @example countVowels("AEIOU") => 5
  */
-
 const countVowels = (str) => {
   if (typeof str !== 'string') {
-    throw new TypeError('Input should be a string')
+    throw new TypeError('Input must be a string')
   }
-
-  const vowelRegex = /[aeiou]/gi
-  const vowelsArray = str.match(vowelRegex) || []
-
-  return vowelsArray.length
+  return (str.match(/[aeiou]/gi) || []).length
 }
 
 export { countVowels }
diff --git a/String/test/CountVowels.test.js b/String/test/CountVowels.test.js
index b05d60e145..e7cd53f6aa 100644
--- a/String/test/CountVowels.test.js
+++ b/String/test/CountVowels.test.js
@@ -1,67 +1,39 @@
-import { countVowels } from '../CountVowels'
+import { countVowels } from '../CountVowels.js'
 
-describe('CountVowels', () => {
-  it('expect throws on use wrong param', () => {
-    expect(() => countVowels(0)).toThrow()
+describe('countVowels', () => {
+  test("countVowels('hello') returns 2", () => {
+    expect(countVowels('hello')).toBe(2)
   })
 
-  it('count the vowels in a string', () => {
-    const value = 'Mad World'
-    const count = countVowels(value)
-    expect(count).toBe(2)
+  test("countVowels('rhythm') returns 0", () => {
+    expect(countVowels('rhythm')).toBe(0)
   })
 
-  it('should return 0 when input is a string with no vowels', () => {
-    const value = 'bcdfgh'
-    const count = countVowels(value)
-    expect(count).toBe(0)
+  test("countVowels('AEIOU') returns 5", () => {
+    expect(countVowels('AEIOU')).toBe(5)
   })
 
-  it('should return 1 when input is a string of length 1 that is a vowel', () => {
-    const value = 'a'
-    const count = countVowels(value)
-    expect(count).toBe(1)
+  test("countVowels('') returns 0", () => {
+    expect(countVowels('')).toBe(0)
   })
 
-  it('should return the correct result when input is in all uppercase letters', () => {
-    const value = 'ABCDE'
-    const count = countVowels(value)
-    expect(count).toBe(2)
+  test("countVowels('The quick brown fox') returns 5", () => {
+    expect(countVowels('The quick brown fox')).toBe(5)
   })
 
-  it('should return the correct result when input is in all lowercase letters', () => {
-    const value = 'abcdefghi'
-    const count = countVowels(value)
-    expect(count).toBe(3)
+  test('countVowels ignores non-letter characters', () => {
+    expect(countVowels('a1e2i3o4u5')).toBe(5)
   })
 
-  it('should return the correct result when input string contains spaces', () => {
-    const value = 'abc def   ghi'
-    const count = countVowels(value)
-    expect(count).toBe(3)
+  test("countVowels('bcdfg') returns 0", () => {
+    expect(countVowels('bcdfg')).toBe(0)
   })
 
-  it('should return the correct result when input contains number characters', () => {
-    const value = 'a1b2c3'
-    const count = countVowels(value)
-    expect(count).toBe(1)
+  test('throws TypeError for non-string input', () => {
+    expect(() => countVowels(123)).toThrow(TypeError)
   })
 
-  it('should return the correct result when input contains punctuation characters', () => {
-    const value = 'a!b.ce)'
-    const count = countVowels(value)
-    expect(count).toBe(2)
-  })
-
-  it('should return 0 when the input is an empty string', () => {
-    const value = ''
-    const count = countVowels(value)
-    expect(count).toBe(0)
-  })
-
-  it('should count multiple occurrences of the same vowel in the input', () => {
-    const value = 'aaaaa'
-    const count = countVowels(value)
-    expect(count).toBe(5)
+  test('throws TypeError for null input', () => {
+    expect(() => countVowels(null)).toThrow(TypeError)
   })
 })