Let’s take for example an incredibly simple code and imagine that it’s incredibly complicated logic. def cat(left, right): """Concatenate two given strings. """ return left + right Tests How can we be sure this code works? No, it’s not obvious. Remember the rules of the game, we have an incredibly complicated realization. So, we can’t say it works or not while we haven’t tested it. def test_cat(): result = cat(left='abc', right='def') assert result == 'abcdef' Now, run pytest:
