Asynchronous unit test helpers

async-unit-tests.m

@property (nonatomic, strong) dispatch_semaphore_t waitSemaphore

- (void)setUp {
    [super setUp];
    
    // Set-up code here.
    
    self.waitSemaphore = dispatch_semaphore_create(0);
}

- (void)waitForAsynchronousTask:(int)waitTimeInSeconds {
    NSDate *timeoutDate = [NSDate dateWithTimeIntervalSinceNow:waitTimeInSeconds];
    while (dispatch_semaphore_wait(self.waitSemaphore, DISPATCH_TIME_NOW)) {
        [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:timeoutDate];
        NSLog(@"waiting for response...");
        if (timeoutDate == [timeoutDate earlierDate:[NSDate date]]) {
            XCTAssertTrue(NO, @"Waiting for a response took longer than %dsec", waitTimeInSeconds);
            return;
        }
    }
}

- (void)completeAsynchronousTask {
    dispatch_semaphore_signal(self.waitSemaphore);
}