When we run those tests (e.g., TestWebKitAPI.WKWebViewCloseAllMediaPresentations.VideoFullscreen), there will be a following warning: *** Warning: <AVPlayerViewController: 0x7f8e0f024000> is trying to enter full screen, but is not in its view's window's view controller hierarchy. This results in undefined behavior. And there will be no fullscreen video on the screen (or simulator) when we run the test.
<rdar://problem/64898125>