使用通知的设计的单元测试

Question

我在测试一些使用通知的逻辑时遇到困难。我读过强制执行特定的NSNotifications已发送，但这并不能真正解决我所看到的问题。

[SomeObject PerformAsyncOperation] 创建一个 NSURLRequest 并将其自身设置为响应委托。根据响应的内容，SomeObject 将成功或失败的 NSNotification 发布到默认的 NSNotificationCenter。

我的测试的问题是，调用 PerformAsyncOperation 后，测试不会等待发送响应。相反，它继续断言 - 该断言失败，因为请求/响应没有时间发送/接收/解析。

代码如下：

-(void)testMethod {
    SomeObject *x = [[SomeObject alloc] init];

    [[NSNotificationCenter defaultCenter] addObserver:self
                                        selector:@selector(success:)
                                            name:SomeObjectSuccess
                                          object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self
                                        selector:@selector(failure:)
                                            name:SomeObjectFailure
                                          object:nil];

    operationCompleted = false; // declared in .h

    [x PerformAsyncOperation:@"parameter"];

    STAssertTrue(operationCompleted , @"Operation has completed.");

    [[NSNotificationCenter defaultCenter] removeObserver:self name:SomeObjectSuccess object:nil];
    [[NSNotificationCenter defaultCenter] removeObserver:self name:SomeObjectFailure object:nil];

    [x release];
}

-(void) failure:(NSNotification *) notification {
   operationCompleted = true;
   NSLog(@"Received failure message.");
}

-(void) success:(NSNotification *) notification {
   operationCompleted = true;
   NSLog(@"Received success message.");
}

我尝试在调用 PerformAsyncOperation 以及空的 while (!operationCompleted) 循环后休眠线程。两者都不起作用 - 睡眠线程仍然无法断言，并且 while 循环永远不会退出。我还尝试将断言移至 success: 和 failure: 中，但由于 OCUnit 期望每个方法都是测试方法，因此它只是立即执行所有三个方法并退出（无需等待 NSURLRequest 的响应，这就是练习的重点！）。

任何想法或见解将不胜感激。谢谢！

Answer 1

您面临的问题不是通知，而是同步的。相反，您正在触发异步操作。为了使其成为可重复的测试，您需要重新同步。

NSTimeInterval timeout = 2.0;   // Number of seconds before giving up
NSTimeInterval idle = 0.01;     // Number of seconds to pause within loop
BOOL timedOut = NO;

NSDate *timeoutDate = [[NSDate alloc] initWithTimeIntervalSinceNow:timeout];
while (!timedOut && !operationCompleted)
{
    NSDate *tick = [[NSDate alloc] initWithTimeIntervalSinceNow:idle];
    [[NSRunLoop currentRunLoop] runUntilDate:tick];
    timedOut = ([tick compare:timeoutDate] == NSOrderedDescending);
    [tick release];
}
[timeoutDate release];

除此之外，您知道操作已完成，或者测试已超时。

Answer 2

为简单起见，如果可能，请使用同步网络请求。

- (void)testExample
{
    [self measureBlock:^{

        NSURLRequest *request = [[NSURLRequest alloc] initWith...];

        NSHTTPURLResponse *response = nil;
        NSData *data = [NSURLConnection sendSynchronousRequest:request
                                         returningResponse:&response
                                                     error:nil];

        XCTAssertEqual(response.statusCode,200);

        // process the data from response ... call the delegate methods or whatever

        NSObject *object = [NSJSONSerialization JSONObjectWithData:data
                                                       options:NSJSONReadingMutableContainers
                                                         error:nil];
        XCTAssertTrue([object isKindOfClass:[NSArray class]]);
    }];
}