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我正在尝试编写一个测试来验证我的场景中的 SKSpriteNode 具有正确的纹理。测试看起来像这样：

let sceneSprite = scene.childNodeWithName("sceneSprite") as SKSpriteNode!

let sprite = SKSpriteNode(imageNamed: expectedSpriteTexture)
sprite.size = sceneSprite.size // 102.4 x 136.533

XCTAssertTrue(sceneSprite.texture!.sameAs(sprite.texture!), "Scene sprite has wrong texture")

SKTexture的sameAs方法通过以下扩展实现：

extension SKTexture {
    func sameAs(texture: SKTexture) -> Bool {
        return self.image.sameAs(texture.image)
    }

    var image: UIImage {
        let view = SKView(frame:CGRectMake(0, 0, size().width, size().height))
        let scene = SKScene(size: size())
        let sprite  = SKSpriteNode(texture: self)
        sprite.position = CGPoint(x: CGRectGetMidX(view.frame), y: CGRectGetMidY(view.frame))
        scene.addChild(sprite)
        view.presentScene(scene)
        return self.imageWithView(view)
    }

    func imageWithView(view: UIView) -> UIImage {
        UIGraphicsBeginImageContextWithOptions(view.bounds.size, view.opaque, 0.0)
        view.drawViewHierarchyInRect(view.bounds, afterScreenUpdates: true)
        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return image
    }
}

extension UIImage {
    func sameAs(image: UIImage) -> Bool {
        let firstData = UIImagePNGRepresentation(self);
        let secondData = UIImagePNGRepresentation(image);
        return firstData.isEqual(secondData)
    }
}

问题是有时测试通过，有时测试失败。我已经更改了代码，以便在失败时保存图像，并发现测试失败，因为即使第一个图像是正确的，第二个图像也是完全黑色的。怎样做才能使测试可靠地通过？此故障发生在 iPad2 的模拟器上。

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1 回答 1

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我做了以下更改，它似乎使测试可靠通过

func imageWithView(view: UIView) -> UIImage {
    UIGraphicsBeginImageContext(view.bounds.size)
    view.drawViewHierarchyInRect(view.bounds, afterScreenUpdates: false)
    let image = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    return image
}

人们对为什么这能让测试成功有什么想法？

于 2015-02-08T00:55:53.467 回答