Xcode 4中的SenTestingKit：异步测试？

- (void)testBlockMethod {
    dispatch_semaphore_t semaphore = dispatch_semaphore_create(0);

    // Your block method eg. AFNetworking
    NSURL *url = [NSURL URLWithString:@\"http://httpbin.org/ip\"];
    NSURLRequest *request = [NSURLRequest requestWithURL:url];
    AFJSONRequestOperation *operation = [AFJSONRequestOperation JSONRequestOperationWithRequest:request success:^(NSURLRequest *request, NSHTTPURLResponse *response, id JSON) {
        NSLog(@\"IP Address: %@\", [JSON valueForKeyPath:@\"origin\"]);
        STAssertNotNil(JSON, @\"JSON not loaded\");
        // Signal that block has completed
        dispatch_semaphore_signal(semaphore);
    } failure:nil];
    [operation start];

    // Run loop
    while (dispatch_semaphore_wait(semaphore, DISPATCH_TIME_NOW))
        [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode
                                 beforeDate:[NSDate dateWithTimeIntervalSinceNow:10]];
    dispatch_release(semaphore);

WAIT_WHILE(<expression_to_evaluate>, <max_duration>);

- (void)testDoSomething {

    __block BOOL somethingIsDone = NO;

    [MyObject doSomethingAsyncThenRunCompletionBlockOnMainQueue:^{
        somethingIsDone = YES;
    }];

    WAIT_WHILE(!somethingIsDone, 1.0); 
    NSLog(@\"This won\'t be reached until async job is done\");
}