Do you put unit tests in same project or another project?

Question

Do you put unit tests in the same project for convenience or do you put them in a separate assembly?

If you put them in a separate assembly like we do, we end up wit

Answer 1

I do not understand the frequent objection to deploying tests with production code. I led a team at a small microcap (grew from 14 to 130 people). We had a half-dozen or so Java apps and we found it EXTREMELY valueable to deploy tests into the field to execute them on a specific machine that was exhibiting unusual behavior. Random problems occur in the field and being able to throw a few thousand unit tests at the mystery with zero cost was invaluable and often diagnosed problems in minutes...including installation problems, flaky RAM problems, machine-specific problems, flaky network problems, etc, etc. I think it is incredibly valuable to put tests into the field. Also, random problems pop up at random times and it is nice to have the unit tests sitting there already waiting to be executed at a moments notice. Hard-drive space is cheap. Just like we try to keep data and functions together (OO design), I think there is something fundamentally valuable in keeping code and tests together (function + tests that validate the functions).

I would like to put my tests in the same project in C#/.NET/Visual Studio 2008, but I still haven't investigated this enought to achieve it.

One big benefit of keeping Foo.cs in the same project as FooTest.cs is that developers are constantly reminded when a class is missing a sibling test! This encourages better test-driven coding practices...holes are more apparent.