使用XCTest将图像添加到ALAssetsLibrary

Question

I have an app that uses photos extensively, making several operations on them:

• resizing
• cropping
• metadata extraction

Most of the methods I wrote operate on AlAssets therefore I would like to write my tests (I'm using the new XCTest framework) to operate also on ALAssets.

I included in the project a set of photos to be used as input to the tests, I was planning on adding every single image to the library on [XCTest +setUp] and remove them on [XCTest +tearDown].

Everything went smoothly - while, kind of, it was a nightmare to have XCTest compiling - however for every call I make to:

- (void)writeImageDataToSavedPhotosAlbum:metadata:completionBlock:

The completion block never, ever, gets called and no image is added to the library, if later on, i enumerate all the photos there, I'll only see the photos that were previously available on the library.

In order to make sure the completion block runs, I control the app flow using semaphores, like this:

UIImage *image = [self imageWithName:@"DSC_0002" extension:@"JPG"];
NSData *dataJpeg = UIImageJPEGRepresentation(image, 0.9f);
ALAssetsLibrary* library = [[ALAssetsLibrary alloc] init];
dispatch_semaphore_t sem = dispatch_semaphore_create(0);
[library writeImageDataToSavedPhotosAlbum:dataJpeg metadata:nil completionBlock:^(NSURL *assetURL, NSError *error) {
        // control will never run this code
        NSLog(@"Asset URL %@",[assetURL absoluteString]);
        dispatch_semaphore_signal(sem);
    }];
dispatch_semaphore_wait(sem, DISPATCH_TIME_FOREVER);

Any ideas ? Any possibility that it's impossible to write on the library on a XCTest ?

Thanks in advance, Ze

Answer 1

You can stop the test method from exiting before the block executes by firing a runloop until a condition is met. Here is an example:

- (void)testAssetLibraryOperation
{
    NSURL *assetURL; // get this however you want
    ALAssetsLibrary *lib =  [ALAssetsLibrary new];

    __block BOOL waiting = YES;

    [lib assetForURL:assetURL resultBlock:^(ALAsset *asset) {

        // perform tests on asset
        XCTAssertNotNil(asset, @"asset should not be nil");

        // stop waiting
        waiting = NO;

    } failureBlock:nil];


    // wait until BOOL says NO
    while (waiting) {
        [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate dateWithTimeIntervalSinceNow:0.1]];
    }
}

You might want to add logic to stop waiting if the operation takes too long.

Also you can checkout these resources on GitHub for more info and inspiration

• https://gist.github.com/azu/7003177
• AsyncXCTestingKit