In SwiftUI, how can we make a Spacer() temporarily visible for debugging?

I have tried:

ZStack{
    Spacer()
    Color.pink
}

(behaves exactly and .pink alone would have)

and…

Spacer()
    .overlay(.pink)

(does nothing)

and…

Spacer()
    .background(.pink)

(does nothing)

None of these seem to work.