What's the best way to structure unit tests in solutions?

Question

I'm working on a C# .net project using Visual Studio 2008, so my question is specifically for this case. However, the question should be the same to many other environments, so I'll be glad to hear opinions from people in similar environments.

My solution is organized in several projects. All of which have some belonging unit tests. There are several ways the tests can be structured, and I've felt the best way to handle this was to have one corresponding ".Tests"-project pr project. I.e. I have the projects:

MyApp.Model
MyApp.Utils

Giving me the corresponding projects for the tests;

MyApp.Model.Tests
MyApp.Utils.Tests

This very nicely wraps all tests that longs together into one project, giving one assembly for each "group" of tests. I've felt comfortable with this being the best way for a while, but as the application grows I get 2 new projects instead of one each time I add a new one. Now I think it's starting to get messy, and I'm considering to add one single MyApp.Tests project to hold all my tests. The tests can still be nicely structured with a good file structure inside this project.

So; how are people structuring their tests?

Answer 1

1 project for ALL tests.

Then comes folders & namespaces integration/unit/regression => then project1/project2/project2.

Configure your test runner to run only unit tests (i.e. - by namespace) and that's it!
Faster build time yet still nicely structured solution guaranteed (of course there are always exclusions where this approach might not be appropriate).

Answer 2

I usually follow the same structure as you do here. It gives a nice consistent pattern where you get the corresponding test directly beneath the project that is tested in the Solution Explorer. Makes it easy to navigate and find out where the tests are located and what code is beeing tested. Also makes it easier for other people who are familliar with this structure to get into your code.

If you have a problem with too many projects, you should use folders more actively. Group the projects (and their tests) into well named and well structured folders.

Answer 3

For each project a separate test project, i.e. Project.Tests. Then I store all my test projects in a single Solution Folder, i.e. "Test Projects".