Unit test the DAO layer at all?

How do you experienced developers comment these lines by Michael Feathers:

A test is not a unit test if:

  • It talks to the database
  • It communicates across the network
  • It touches the file system
  • It can't run at the same time as any of your other unit tests
  • You have to do special things to your environment (such as editing config. files) to run it.

Now I was wondering if I should unit test my DAO classes... Will I get more advantages or disadvantages by unit testing the DAO layer? Share your thoughts please.


Feathers isn't saying don't write such tests. He's saying they're not unit tests, because he defines a unit test as "small, they test a method or the interaction of a couple of methods. ... a "binary chop" that allows you to discover whether the problem is in your logic or in the things are you interfacing with." And he's right - the Agile/XP/Scrum intention of unit testing is to provide a fast red light/green light determination if a small piece of code is functioning correctly.

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