hillCipher.test.js

import { hillCipherEncrypt, hillCipherDecrypt } from '../hillCipher';

describe('hillCipher', () => {
  it('should throw an exception when trying to decipher', () => {
    expect(hillCipherDecrypt).toThrowError('This method is not implemented yet');
  });

  it('should throw an error when message or keyString contains none letter character', () => {
    const invalidCharacterInMessage = () => {
      hillCipherEncrypt('hell3', 'helloworld');
    };
    const invalidCharacterInKeyString = () => {
      hillCipherEncrypt('hello', 'hel12world');
    };
    expect(invalidCharacterInMessage).toThrowError(
      'The message and key string can only contain letters',
    );
    expect(invalidCharacterInKeyString).toThrowError(
      'The message and key string can only contain letters',
    );
  });

  it('should throw an error when the length of the keyString has a square root which is not integer', () => {
    const invalidLengthOfKeyString = () => {
      hillCipherEncrypt('ab', 'ab');
    };
    expect(invalidLengthOfKeyString).toThrowError(
      'Invalid key string length. The square root of the key string must be an integer',
    );
  });

  it('should throw an error when the length of the keyString does not equal to the power of length of the message', () => {
    const invalidLengthOfKeyString = () => {
      hillCipherEncrypt('ab', 'aaabbbccc');
    };
    expect(invalidLengthOfKeyString).toThrowError(
      'Invalid key string length. The key length must be a square of message length',
    );
  });

  it('should encrypt passed message using Hill Cipher', () => {
    expect(hillCipherEncrypt('ACT', 'GYBNQKURP')).toBe('POH');
    expect(hillCipherEncrypt('CAT', 'GYBNQKURP')).toBe('FIN');
    expect(hillCipherEncrypt('GFG', 'HILLMAGIC')).toBe('SWK');
  });
});