text: 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');
    });
  });
  