snapshot containing SwiftUI liquid glass effect is fully transparent

[lukaskollmer]

Describe the bug
snapshot-testing a SwiftUI view that contains a glass effect always results in a fully transparent snapshot image.

To Reproduce

@MainActor @Test
func example() async throws {
    // view without glass effect. this will work fine.
    let view1 = Button("Tap Me") {}
        .buttonStyle(.borderedProminent)
    assertSnapshot(of: view1, as: .image(layout: .device(config: .iPhone13Pro)), named: "1")

    // view glass effect. this will produce a transparent snapshot.
    let view2 = Button("Tap Me") {}
        .buttonStyle(.glassProminent)
    assertSnapshot(of: view2, as: .image(layout: .device(config: .iPhone13Pro)), named: "2")
}

of the two resulting images, example.1.png is correct, but example.2.png is just a transparent PNG.

Expected behavior
the view containing a glass effect should still render correctly.

Environment

• swift-snapshot-testing version 1.18.7
• Xcode 26
• Swift 6.2
• OS: host is macOS 15.6.1; tests are running in iOS 26 simulator

Additional context
#1019 is very likely a closely related bug, but i'm not sure if it's the same since

• they put focus on this being related to the tintColor and backgroundColor of the view (which seems to be irrelevant here), and
• they are using UIKit and a UIEffectView whereas the example here is pure SwiftUI (which, looking at the specific view hierarchy at runtime, doesn't seem to be using any UIEffectViews...)

[ibrahimFever]

+1

[stephencelis]

@lukaskollmer @ibrahimFever Snapshotting views with effects (like liquid glass) requires an application test host and explicit enabling of the drawHierarchyInKeyWindow parameter in the snapshot strategy. Have you tried that?

[angu-software]

Woks with a HostApp and drawing using drawHierarchyInKeyWindow.

This is a bummer actually, because we rely basically on system components in our component swift package. So testing will always need a snapshot host app now with Liquid Glass around because now most of the UI elements will have am effect applied.

[mbrandonw]

It's a bummer, but sadly just how Apple's tools work, and there's not much we can do about it.

Since this isn't an issue with the library I am going to convert it to a discussion. Please feel free to continue the conversation over there!