GHTestCase+Swizzle.h

@class GHTestCase;

@interface GHTestCase (Swizzle)

+ (id)sharedMock;
+ (void)setSharedMock:(id)newMock;

- (void)swizzle:(Class)target_class selector:(SEL)selector;
- (void)deswizzle;

@end

GHTestCase+Swizzle.m

#import "GHUnit.h"
#import "GHTestCase+Swizzle.h"
#import <objc/objc-runtime.h>

id sharedMockPointer = nil;

@implementation GHTestCase (Swizzle)

+(id)sharedMock
{
	return sharedMockPointer;
}

+(void)setSharedMock:(id)newMock
{
	sharedMockPointer = newMock;
}

Method originalMethod = nil;
Method swizzleMethod = nil;

- (void)swizzle:(Class)target_class selector:(SEL)selector
{
	originalMethod = class_getClassMethod(target_class, selector);
	swizzleMethod = class_getInstanceMethod([self class], selector);
	method_exchangeImplementations(originalMethod, swizzleMethod);
}

- (void)deswizzle
{
	method_exchangeImplementations(swizzleMethod, originalMethod);
	swizzleMethod = nil;
	originalMethod = nil;
}

@end

Hi I found your gist while searching for testing of the Class methods, it inspired me to implement the same concepts with blocks: git://gist.github.com/1038034.git

Thanks for sharing!

That is awesome! Thanks for the update with blocks.

Fantastic.

I had trouble compiling this for the simulator (Xcode 4.2).

If you change

#import <objc/objc-runtime.h 

to

#import <objc/runtime.h>

this will compile and run in both the simulator and devices.

Sorry for the multiple edits - goofed on the formatting.