Xcode 4 unit testing linker error

Question

NOTE: "Use GHUnit" is not an acceptable answer to this question. I know most think GHUnit is better than the Xcode4 OCUnit, but that's not what I'm asking about. I'll evaluate that separately.

I have an Xcode project that I created in Xcode4 from scratch, with the "Include unit tests" checkbox checked during creation. I have also included some libraries I developed in a previous project. They were added to the project via the "Add Files to x..." dialog and only added to the application target (not the testing target). They work fine when running the application, so I think they're set up correctly. I also have a number of various classes written for this project.

My testing files are set up in the standard way, named [AppName]Tests.h and .m.
Code for header:
#import < SenTestingKit/SenTestingKit.h >

@interface [AppName]Tests : SenTestCase {
@private
}
@end

Code for implementation:
#import "[AppName]Tests.h"

@implementation [AppName]Tests

- (void)setUp
{
    [super setUp];
    // Set-up code here.
}

- (void)tearDown
{
    // Tear-down code here.
    [super tearDown];
}  
// Test methods go here
@end

Which is just the basic skeleton. It works fine in my other project, and in this project as long as I don't import any other files. When I do import another file from this project and use it, I see the following error in the Xcode output log:
The test bundle at /Users/[Me]/Library/Developer/Xcode/DerivedData/[AppName]-dwuuuwcpmdqxqmgxomoniplwhlpb/Build/Products/Debug-iphonesimulator/[AppName]Tests.octest could not be loaded because a link error occurred. It is likely that dyld cannot locate a framework framework or library that the the test bundle was linked against, possibly because the framework or library had an incorrect install path at link time.

I've already verified that:

1. All the frameworks I use have been added to "Link Binary with Libraries" for both the app and test targets.
2. The test target has been configured to build correctly and that all my test methods show up in Edit Scheme...->Test->Tests
3. Every issue but this one has been resolved and there are no compiler errors.
4. All the settings discussed here are set up correctly and identical to my other project that tests correctly.

Any thoughts on what might be causing this?

Answer 1

I had this same problem once. For some reason one of the source files for my project was also included to be compiled for the test target, which causes this link error.

By making sure that only the test-implementation files are compiled, you should be able to resolve this error. You can check this at:

TestTarget -> Build Phases -> Compile Sources

Answer 2

When I get linker errors running unit tests, two things fix the problem for me. The first solution is to set the Test After Build build setting to YES and choose Product > Build For > Build For Testing to run the tests. This solution is the easier one to implement.

The second solution is to add the application's implementation files to the unit test target. Open the file inspector by choosing View > Utilities > File Inspector. Select an implementation file in the project navigator. Select the checkbox next to the unit test target in the file inspector.

For iPhone applications running in the simulator, make sure the Test Host build setting is blank. The simulator does not support application-hosted unit tests.

Answer 3

I just wasted hours on this and similar errors - turns out I had renamed my main target - attempts to fix this by renaming the relevant variables and by removing the entire DerivedData directory were unsuccessful.

I eventually simply set up a new unit test target following the steps here: http://twobitlabs.com/2011/06/adding-ocunit-to-an-existing-ios-project-with-xcode-4/

And everything is fine now.

So - if you have strange, inexplicable link errors you might be better off just creating a new unit test target. Only takes 2 minutes.