diff --git a/src/_Classics_/caesar_cipher/caesarCipher.test.js b/src/_Classics_/caesar_cipher/caesarCipher.test.js
new file mode 100644
index 00000000..cfa68026
--- /dev/null
+++ b/src/_Classics_/caesar_cipher/caesarCipher.test.js
@@ -0,0 +1,67 @@
+/* eslint-disable linebreak-style */
+/* eslint-disable no-else-return */
+const caesarCipher = require('./caeserCipher');
+
+describe('Caesar Cipher tests', () => {
+  it('Shift not passed', () => {
+    const ocString = 'Hello World';
+    const enCiphered = caesarCipher(ocString);
+    expect(ocString).toBe(enCiphered);
+  });
+
+  it('Encipher equals decipher', () => {
+    const ocString = 'Hello World';
+    const enCiphered = caesarCipher(ocString, 1);
+    const deCiphered = caesarCipher(enCiphered, -1);
+    expect(ocString).toBe(deCiphered);
+  });
+
+  it('Shift lower than string length works', () => {
+    const ocString = 'Hello World';
+    const enCiphered = caesarCipher(ocString, 1);
+    const idealResult = 'Ifmmp Xpsme';
+    expect(enCiphered).toBe(idealResult);
+  });
+
+  it('Shift Higher than string length works', () => {
+    const ocString = 'Hello World';
+    const enCiphered = caesarCipher(ocString, 63);
+    const idealResult = caesarCipher(ocString, 1);
+    expect(enCiphered).toBe(idealResult);
+  });
+
+  it('Negative shift Works', () => {
+    const ocString = 'Ifmmp Xpsme';
+    const enCiphered = caesarCipher(ocString, -1);
+    const idealResult = 'Hello World';
+    expect(enCiphered).toBe(idealResult);
+  });
+
+  it('Shift is a numerical string', () => {
+    const ocString = 'Hello World';
+    const enCiphered = caesarCipher(ocString, '1');
+    const idealResult = 'Ifmmp Xpsme';
+    expect(enCiphered).toBe(idealResult);
+  });
+
+  it('Shift is not a numbered string', () => {
+    function test() {
+      caesarCipher('Hello World', 'abc');
+    }
+    expect(test).toThrow('Invalid Shift Provided');
+  });
+
+  it('toEncipher is NaN', () => {
+    function test() {
+      caesarCipher(NaN, 1);
+    }
+    expect(test).toThrowError('Invalid string provided');
+  });
+
+  it('toEncipher is undefined', () => {
+    function test() {
+      caesarCipher(undefined, 1);
+    }
+    expect(test).toThrowError('Invalid string provided');
+  });
+});
diff --git a/src/_Classics_/caesar_cipher/caeserCipher.js b/src/_Classics_/caesar_cipher/caeserCipher.js
new file mode 100644
index 00000000..3988dafe
--- /dev/null
+++ b/src/_Classics_/caesar_cipher/caeserCipher.js
@@ -0,0 +1,46 @@
+/**
+ * Most simplest encryption scheme. Read more: [http://practicalcryptography.com/ciphers/caesar-cipher/]
+ **/
+function caesarCipher(toEncipher, shift = 0) {
+  // If required for very strict shift checking then remove '=0'
+  if (Number.isNaN(Number(shift)) === true) {
+    throw new Error('Invalid Shift Provided');
+  } else {
+    shift = parseInt(Number(shift), 10);
+  }
+
+  if (typeof (toEncipher) === 'string' || (typeof (toEncipher) === 'number' && Number.isNaN(toEncipher) === false)) {
+    toEncipher = String(toEncipher);
+  } else {
+    throw new Error('Invalid string provided');
+  }
+
+  // These are the valid entries aacepted, you can change it according to requirements
+  const validEntries = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';
+
+  shift %= validEntries.length;
+
+  let output = '';
+  for (const char of toEncipher) {
+    if (char === ' ') {
+      output += ' ';
+      continue;
+      // ------- If you donot want to accept invalid entries then uncomment below block
+    /*
+    ========================================================================================================
+            } else if (validEntries.indexOf(char) === -1) {return Error ('invalid character' + char)}
+    ========================================================================================================
+    and comment out the below block
+    */
+      //= ======================================================================================================
+    } else if (validEntries.indexOf(char) === -1) {
+      output += char;
+      continue;
+    }
+    //= ======================================================================================================
+    output += (validEntries.indexOf(char) + shift <= validEntries.length) ? validEntries[validEntries.indexOf(char) + shift] : validEntries[(validEntries.indexOf(char) + shift) % validEntries.length];
+  }
+  return output;
+}
+
+module.exports = caesarCipher;
diff --git a/src/_Classics_/caeser_cipher/index.js b/src/_Classics_/caeser_cipher/index.js
deleted file mode 100644
index 8851bf03..00000000
--- a/src/_Classics_/caeser_cipher/index.js
+++ /dev/null
@@ -1,61 +0,0 @@
-/**
- * Most simplest encryption scheme. Read more: [http://practicalcryptography.com/ciphers/caesar-cipher/]
- * @param {String} str
- * @param {Number} num
- */
-
-function caesarCipher(str, num) {
-  if (!num) throw new Error('Missing argument: num');
-
-  const lowerCaseString = str.toLowerCase();
-  const alphabets = 'abcdefghijklmnopqrstuvwxyz'.split('');
-  const totalAlphabets = alphabets.length;
-  let result = '';
-
-  // handle large number, like 300 or -300
-  num %= totalAlphabets;
-
-  const alphabetsMap = new Map();
-
-  for (const index in alphabets) {
-    alphabetsMap[alphabets[index]] = index;
-  }
-
-  for (let index in lowerCaseString) {
-    // get the current character
-    const currentCharacter = lowerCaseString[index];
-
-    // if character is space, add it to the result and continue to next
-    if (currentCharacter === ' ') {
-      result += currentCharacter;
-      continue;
-    }
-
-    // determine the new index
-    /**
-     * const currentIndex = alphabets.indexOf(currentCharacter);
-     *
-     * With indexOf complexity will be O(n*26)
-     * With Map complexity will be O(n).
-     */
-    const currentIndex = Number(alphabetsMap[currentCharacter]);
-    let newIndex = currentIndex + num;
-
-    // if the index passes 25, restart from 0
-    if (newIndex > totalAlphabets - 1) {
-      newIndex -= totalAlphabets;
-    }
-
-    if (newIndex < 0) {
-      newIndex = totalAlphabets + newIndex;
-    }
-
-    // check if the character in original string was upper case
-    if (str[index] === str[index].toUpperCase()) {
-      result += alphabets[newIndex].toUpperCase();
-    } else {
-      result += alphabets[newIndex];
-    }
-  }
-  return result;
-}