Based on https://gist.github.com/2215212, a method helper to unit test AFNetworking operations in SenTestingKit.

gistfile1.m

// Call theResume() to stop the semaphore from blocking/waiting.
// Failure to call theResume() will cause the test to hang.
// This is needed to test asynchronous operations. See https://gist.github.com/2215212
- (void)dispatchSemaphoreInBlock:(void (^)(void (^theResume)(void)))theBlock {
    dispatch_semaphore_t theSemaphore = dispatch_semaphore_create(0);
    theBlock(^{ dispatch_semaphore_signal(theSemaphore); });
    while (dispatch_semaphore_wait(theSemaphore, DISPATCH_TIME_NOW)) {
        [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate dateWithTimeIntervalSinceNow:0.1]];
    }
    dispatch_release(theSemaphore);
}

// The unit test: Fail to succeed...
- (void)testDispatchSemaphoreInBlock {
    // How it should have worked...
    {
        AFHTTPClient *theHTTPClient = [[AFHTTPClient alloc] initWithBaseURL:[NSURL URLWithString:@"http://www.google.com/"]];
        [theHTTPClient
         getPath:@""
         parameters:nil
         success:^(AFHTTPRequestOperation *operation, id responseObject) {
             STFail(@"This will not fail when it should...");
         }
         failure:^(AFHTTPRequestOperation *operation, NSError *error) {
             STFail(@"This will not fail when it should...");
         }];
    }

    // The workaround with dispatchSemaphoreInBlock method...
    [self dispatchSemaphoreInBlock:^(void (^theResume)(void)) {
        AFHTTPClient *theHTTPClient = [[AFHTTPClient alloc] initWithBaseURL:[NSURL URLWithString:@"http://www.google.com/"]];
        [theHTTPClient
         getPath:@""
         parameters:nil
         success:^(AFHTTPRequestOperation *operation, id responseObject) {
             STFail(@"This will fail...");
             theResume();
         }
         failure:^(AFHTTPRequestOperation *operation, NSError *error) {
             STFail(@"This will fail...");
             theResume();
         }];
    }];
}