My GUESS was that he/she means that the code has asserts in it that check if something is not right at runtime. I personally would not call that a replacement/alternative for unit tests. In fact, it may be counterproductive ... a small error in the code would bring down and entire application.

Assert driven testing means that the tests are part of the actual code that is running. It's helpful because when an assert fails, the stack trace is right at the position where it failed. In many ways it's an easy way to incorporate testing into your application without the need for an additional framework.

A simple example can be done by writing a single function in the root scope or some global function (javascript)

function assert(assertion, description) { if(!assertion) { console.log(description); //could also have other application error handling code } }

Then in a function in your application:

function myFunc() { var x = 1; assert(x == 1, "x does not equal 1 in myFunc()“);

\\Continue code... }

This is obviously a very simple example and can definitely be iterated upon, but it gets the basic point across and I'm on my phone so writing code isn't the easiest :-P

Some systems have something like this built in, such as node which has more features.

http://nodejs.org/api/assert.html

Sounds like Design by Contract.