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Testing Caesar Cipher Implementation in javascript-algorithms

This test suite validates the Caesar Cipher implementation in JavaScript, covering both encryption and decryption functionality. The tests ensure proper character shifting, case handling, and full phrase processing through comprehensive unit testing.

Test Coverage Overview

The test suite provides thorough coverage of the Caesar Cipher algorithm’s core functionality.

  • Zero shift validation
  • Multiple shift values testing
  • Case sensitivity handling
  • Empty string processing
  • Special character preservation
  • Full phrase encryption/decryption

Implementation Analysis

The testing approach utilizes Jest’s describe/it pattern for organized test structure. Each test case focuses on specific cipher characteristics, employing expect().toBe() assertions for precise output validation.

The implementation verifies both encryption and decryption methods, ensuring bidirectional functionality works correctly across various input scenarios.

Technical Details

Testing Framework: Jest

  • Import/export module system for cipher functions
  • Describe blocks for logical test grouping
  • Individual test cases using it() blocks
  • Assertion-based verification using expect()

Best Practices Demonstrated

The test suite exemplifies strong testing practices through modular organization and comprehensive coverage.

  • Isolated test cases for specific functionality
  • Edge case handling
  • Symmetric testing of encryption/decryption
  • Clear test descriptions
  • Consistent assertion patterns

trekhleb/javascript-algorithms

src/algorithms/cryptography/caesar-cipher/__test__/caesarCipher.test.js

            
import { caesarCipherEncrypt, caesarCipherDecrypt } from '../caesarCipher';

describe('caesarCipher', () => {
  it('should not change a string with zero shift', () => {
    expect(caesarCipherEncrypt('abcd', 0)).toBe('abcd');
    expect(caesarCipherDecrypt('abcd', 0)).toBe('abcd');
  });

  it('should cipher a string with different shifts', () => {
    expect(caesarCipherEncrypt('abcde', 3)).toBe('defgh');
    expect(caesarCipherDecrypt('defgh', 3)).toBe('abcde');

    expect(caesarCipherEncrypt('abcde', 1)).toBe('bcdef');
    expect(caesarCipherDecrypt('bcdef', 1)).toBe('abcde');

    expect(caesarCipherEncrypt('xyz', 1)).toBe('yza');
    expect(caesarCipherDecrypt('yza', 1)).toBe('xyz');
  });

  it('should be case insensitive', () => {
    expect(caesarCipherEncrypt('ABCDE', 3)).toBe('defgh');
  });

  it('should correctly handle an empty strings', () => {
    expect(caesarCipherEncrypt('', 3)).toBe('');
  });

  it('should not cipher unknown chars', () => {
    expect(caesarCipherEncrypt('ab2cde', 3)).toBe('de2fgh');
    expect(caesarCipherDecrypt('de2fgh', 3)).toBe('ab2cde');
  });

  it('should encrypt and decrypt full phrases', () => {
    expect(caesarCipherEncrypt('THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG', 23))
      .toBe('qeb nrfzh yoltk clu grjmp lsbo qeb ixwv ald');

    expect(caesarCipherDecrypt('qeb nrfzh yoltk clu grjmp lsbo qeb ixwv ald', 23))
      .toBe('the quick brown fox jumps over the lazy dog');
  });
});