Introduction to Caesar’s cipher

The idea is that you have a shift from 0 to 25, who as the name suggest, shift each letter it’s value, for example, a shift of 3 would output something like:

Plaintext:  THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG
Ciphertext: QEB NRFZH YOLTK CLU GRJMP LSBO QEB IXWV ALD

So it means that to communicate using this cipher, you would receive the message and the shift used to encrypt, so you can decrypt the message.

Writing a test saved me from a wrong feature

While implementing tests for this project (you can find it here), one of the tests was named TestRandomShift and the idea was to test the implementation that assigns a random value to shift between 1 and 25 if 0 was passed.

While implementing this test, I realize a thing:

How I can decrypt the message if I don’t know the shift used?

If I pass shift = 0 the shift would be auto-generated, and I wouldn’t be able to validate if the decrypted text is equal to the input, with that being said I notice how implementing tests can “guard” you from, for example, implement a wrong feature.

I expect this to be one of a series of posts talking about what I learned from writing tests. The repository for the Caesar's cipher project is here.

See you on the next episode.