Unit Testing of Cocoa Apps

February 23, 2006

There’s plenty of articles out there telling you how to use OCUnit, especially now that it ships with XCode 2.0. They’re all excellent. You should read them, especially Apple’s. This article is simply about a little trick that I’ve come up with to solve a minor annoyance I have with using Apple’s method of hooking up what they call a dependent test bundle.

A dependent test bundle is a really neat idea, actually. It uses your actual application as a framework at link time and then uses some nifty magic to launch the test bundle from inside your application and run all of the tests. Why bother with all of that? It means you can keep your application code in one target and your test code in another target – completely separate. That’s a worthy goal.

The only thing I don’t like about this, though, is that if you’re developing a GUI Cocoa application (and let’s face it, most people are) then the process of running the tests from within the application has the consequence of popping up the GUI and letting it sit there until you quit manually. That’s annoying.

So I came up with a solution. It’s really nothing that fancy, but I thought I’d share. I make a Cocoa Shell Tool target, and I name it something like stub. I make a C file and name it stub-main.m. In that file I put the following three lines:

int main(int argc, char *argv[]) {
  return 0;

Then I add all of the application source files that my tests are going to need to link to and make sure it all compiles. I just use that as the bundle loader for my tests, and it’s all good. No GUI popping up.

For an example of how to do this, you can look at the source for OCFit.

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