cryptography_adapter.rb

# lib/cryptography_adapter.rb

# Parent adapter class
class CryptographyAdapter

  def encrypted?(data)
    raise "Method not implmented"
  end
  
  def decrypt(data)
    raise "Method not implmented"
  end
end

cryptography_initializer.rb

# config/initializers/cryptography.rb

Cryptography::cryptography_klass = CryptographyAdapter::GPG

cryptogrophy.rb

# lib/cryptography.rb

# Public interface for your encryption and decryption needs

class Cryptography

  cattr_accessor :cryptography_klass
  attr_reader :crypto
  
  def initialize()
    @crypto = self.class.cryptography_klass.new
  end
  
  def encrypted?(data)
    @crypto.encrypted?(data)
  end
  
  def decrypt(data)
    @crypto.decrypt(data)
  end
  
end

gpg.rb

# lib/cryptography_adapter/gpg.rb

# Used in production
class CryptographyAdapter::GPG < CryptographyAdapter
  
  def encrypted?(data)
    # Return true for encrypted data
  end
  
  def decrypt(data)
   # Decrypt some data
  end
end

rot13.rb

# lib/cryptography_adapter/rot13.rb

# Used in tests
class CryptographyAdapter::ROT13 < CryptographyAdapter

  def encrypted?(data)
    # Return true for encrypted data
  end
  
  def decrypt(data)
    # Decrypt some data
  end
end

test_helper.rb

# test/test_helper.rb

Cryptography::cryptography_klass = CryptographyAdapter::ROT13