Previews that apple showed in wwdc20 "Intdoduce SwiftUI" session. We can test dynamic-type, dark-mode, right-to-left language and location by using it.

AppleStylePreviewView.swift

import SwiftUI

/// Previews that apple show in wwdc20 "Intdoduce SwiftUI" session. We can test dynamic-type, dark-mode, right-to-left language and location by using it.
struct AppleStylePreviewView<Content : View>: View {
    
    var childView: Content
    
    init(@ViewBuilder builder: () -> (Content)) {
        self.childView = builder()
    }
    
    var body: some View {
        Group {
            childView
            childView
                .environment(\.sizeCategory, .extraExtraExtraLarge)
            childView
                .preferredColorScheme(.dark)
                .environment(\.sizeCategory, .extraExtraExtraLarge)
            childView
                .preferredColorScheme(.dark)
                .environment(\.sizeCategory, .extraExtraExtraLarge)
                .environment(\.layoutDirection, .rightToLeft)
                .environment(\.locale, Locale(identifier: "ar"))
            
        }
    }
}

struct AppleStylePreviewView_Previews: PreviewProvider {
    static var previews: some View {
        AppleStylePreviewView {
            Text("Hello world.")
        }
    }
}