diff --git a/src/_Classics_/caeser_cipher/caesar-cipher.test.js b/src/_Classics_/caeser_cipher/caesar-cipher.test.js
new file mode 100644
index 00000000..3b4564a2
--- /dev/null
+++ b/src/_Classics_/caeser_cipher/caesar-cipher.test.js
@@ -0,0 +1,33 @@
+const { caesarCipher } = require('.');
+
+describe('Caesar Cipher test suit', () => {
+  it('Should raise an error when missing second arg', () => {
+    expect(() => { caesarCipher('hello'); }).toThrowError();
+  });
+
+  it('Should raise an error when second arg is not a num', () => {
+    expect(() => { caesarCipher('hello', 'yes'); }).toThrowError();
+  });
+
+  it('Should return a encrypted word with positive num', () => {
+    expect(caesarCipher('character', 10)).toBe('mrkbkmdob');
+  });
+
+  it('Should return the same word/sentence introduced if num = 0', () => {
+    expect(caesarCipher('character', 0)).toBe('character');
+  });
+
+  it('Should return a encrypted word with negative num', () => {
+    expect(caesarCipher('character', '-10')).toBe('sxqhqsjuh');
+  });
+
+  it('Should reuturn a encrypted sentence with spaces', () => {
+    expect(caesarCipher('another one bite the dust', 15))
+      .toBe('pcdiwtg dct qxit iwt sjhi');
+  });
+
+  it('Should return a encrypted sentence with preserved upper case letters', () => {
+    expect(caesarCipher('Another one Bite the Dust', 15))
+      .toBe('Pcdiwtg dct Qxit iwt Sjhi');
+  });
+});
diff --git a/src/_Classics_/caeser_cipher/index.js b/src/_Classics_/caeser_cipher/index.js
index 8851bf03..507eb92e 100644
--- a/src/_Classics_/caeser_cipher/index.js
+++ b/src/_Classics_/caeser_cipher/index.js
@@ -21,7 +21,7 @@ function caesarCipher(str, num) {
     alphabetsMap[alphabets[index]] = index;
   }
 
-  for (let index in lowerCaseString) {
+  for (const index in lowerCaseString) {
     // get the current character
     const currentCharacter = lowerCaseString[index];
 
@@ -59,3 +59,7 @@ function caesarCipher(str, num) {
   }
   return result;
 }
+
+module.exports = {
+  caesarCipher,
+};