GH-Unit for unit testing Objective-C code, why am I getting linking errors?

问题

I'm trying to dive into the quite frankly terrible world of unit testing using Xcode (such a convoluted process it seems.)

Basically I have this test class, attempting to test my Show.h class

#import <GHUnit/GHUnit.h>
#import "Show.h"
@interface ShowTest : GHTestCase { }
@end

@implementation ShowTest
- (void)testShowCreate
{
    Show *s = [[Show alloc] init];
    GHAssertNotNil(s,@"Was nil.");      
}

@end

However when I try to build and run my tests it moans with this error: -

Undefined symbols:

"_OBJC_CLASS_$_Show", referenced from:

 __objc_classrefs__DATA@0 in ShowTest.o

ld: symbol(s) not found

collect2: ld returned 1 exit status

Now I'm presuming this is a linking error. I tried following every step in the instructions located here: -

http://github.com/gabriel/gh-unit/blob/master/README.md

And step 2 of these instructions confused me: -

In the Target 'Tests' Info window, General tab:

Add a linked library, under Mac OS X 10.5 SDK section, select GHUnit.framework

Add a linked library, select your project.

Add a direct dependency, and select your project. (This will cause your application or framework to build before the test target.)

How am I supposed to add my project to the linked library list when all it accepts it .dylib, .framework and .o files?

回答1:

If the target you are testing is an application, you'll need to manually include the Show.h/m files in both your main target and your test target.

I also updated the README to reflect this:

• If your main target is a library: Add a linked library, and select your main target; This is so you can link your test target against your main target, and then you don't have to manually include source files in both targets.
• If your main target is an application, you will need to include these source files in the Test project manually.

Sorry for the confusion! Having to include files in both targets is not ideal.

回答2:

You have to have an @implementation for Show.

Or you could use

Show* s = [[objc_getClass("Show") alloc] init];
...

or

Show* s = [[NSClassFromString(@"Show") alloc] init];
...

to resolving the class in run-time.

回答3:

Somehow Apple's example works without duplicating the .m files in the target.

Download Apple's unit testing sample code (iPhoneUnitTests.zip) here:

http://developer.apple.com/IPhone/library/samplecode/iPhoneUnitTests/Introduction/Intro.html

Click on the CalcTests target. Only CalcTests.m is in this target.

Build the target. It builds without any link errors for CalcAppDelegate or other classes.

What's the magic that makes this work?

来源：https://stackoverflow.com/questions/2610670/gh-unit-for-unit-testing-objective-c-code-why-am-i-getting-linking-errors