The Difference Between Unit Testing and Integration Testing

Roy Osherove is writing a book on Unit Testing and also has made the first chapter of his book available. I like it because it gives a very good description between the difference between Unit Test and Integration Testing (or in our case System Testing).

http://www.manning.com/osherove/Ch1_Unit_Testing.pdf

Highlights from the chapter:

Many people confuse the act of simply testing their software with concept of a unit test. To start off, ask yourself the following questions about the tests you’ve written up to now:

• Can I run and get results of a unit test I wrote two week/months//years ago?
• Can any member of my team run and get the results from unit tests I wrote two months ago?
• Can take me no more than a few minutes to run all the unit test I’ve written so far?
• Can I run unit test I’ve written at the push of a button?
• Can I write a basic unit test in no more than a few minutes?

If you’ve answered any these questions with a “no,” there’s a high probability that what you’re actually implementing is not really a unit test…You’ve done integration testing.

Based on the previous questions, we can map out what properties a unit test should have:

• It is automated and repeatable.
• It is easy to implement.
• Once it’s written, it stays on for the future.
• Anyone can r run it.
• It runs at the push of a button.
• It runs quickly.

The PDF goes into depth on each of the bullets above so if you get the chance check it out.