Quick proposal to fix .wait method

Sources/SnapshotTesting/Common/View.swift

@@ -926,6 +926,48 @@
       }
     }
 
+//<<<<<<< HEAD
+//  if size.width == 0 || size.height == 0 {
+//    // Try to call sizeToFit() if the view still has invalid size
+//    view.sizeToFit()
+//    view.setNeedsLayout()
+//    view.layoutIfNeeded()
+//  }
+//
+//  return dispose
+//}
+//
+//func snapshotView(
+//  config: ViewImageConfig,
+//  drawHierarchyInKeyWindow: Bool,
+//  traits: UITraitCollection,
+//  view: UIView,
+//  viewController: UIViewController,
+//  delay: Double? = nil
+//  )
+//  -> Async<UIImage> {
+//    let initialFrame = view.frame
+//    let dispose = prepareView(
+//      config: config,
+//      drawHierarchyInKeyWindow: drawHierarchyInKeyWindow,
+//      traits: traits,
+//      view: view,
+//      viewController: viewController
+//    )
+//    // NB: Avoid safe area influence.
+//    if config.safeArea == .zero { view.frame.origin = .init(x: offscreen, y: offscreen) }
+//
+//    return (view.snapshot ?? Async { callback in
+//      addImagesForRenderedViews(view).sequence().delay(by: delay).run { views in
+//        callback(
+//          renderer(bounds: view.bounds, for: traits).image { ctx in
+//            if drawHierarchyInKeyWindow {
+//              view.drawHierarchy(in: view.bounds, afterScreenUpdates: true)
+//            } else {
+//              view.layer.render(in: ctx.cgContext)
+//            }
+//          }
+//=======
     func prepareView(
       config: ViewImageConfig,
       drawHierarchyInKeyWindow: Bool,
@@ -970,7 +1012,8 @@
       drawHierarchyInKeyWindow: Bool,
       traits: UITraitCollection,
       view: UIView,
-      viewController: UIViewController
+      viewController: UIViewController,
+      delay: Double? = nil
     )
       -> Async<UIImage>
     {
@@ -988,7 +1031,7 @@
       return
         (view.snapshot
         ?? Async { callback in
-          addImagesForRenderedViews(view).sequence().run { views in
+          addImagesForRenderedViews(view).sequence().delay(by: delay).run { views in
             callback(
               renderer(bounds: view.bounds, for: traits).image { ctx in
                 if drawHierarchyInKeyWindow {

Sources/SnapshotTesting/Extensions/Async+Delay.swift

@@ -0,0 +1,20 @@
+import Foundation
+
+extension Async {
+  /// Delays Async `run` block
+  /// - Parameter timeInterval: Optional duration for Async to wait before running `run`
+  /// - Returns: Delayed `Async` unless no duration was provided then returns original `Async`
+  func delay(by timeInterval: TimeInterval?) -> Async<Value> {
+    guard let timeInterval = timeInterval else {
+      return self
+    }
+
+    return Async<Value> { callback in
+      run { value in
+        DispatchQueue.main.asyncAfter(deadline: .now() + timeInterval) {
+          callback(value)
+        }
+      }
+    }
+  }
+}

Sources/SnapshotTesting/Snapshotting/UIViewController.swift

@@ -7,6 +7,7 @@
       return .image()
     }
 
+
     /// A snapshot strategy for comparing view controller views based on pixel equality.
     ///
     /// - Parameters:
@@ -18,12 +19,14 @@
     ///     human eye.
     ///   - size: A view size override.
     ///   - traits: A trait collection override.
+    ///   - delay: A time in seconds, for how long to wait before making snapshot
     public static func image(
       on config: ViewImageConfig,
       precision: Float = 1,
       perceptualPrecision: Float = 1,
       size: CGSize? = nil,
-      traits: UITraitCollection = .init()
+      traits: UITraitCollection = .init(),
+      delay: Double? = nil
     )
       -> Snapshotting
     {
@@ -37,7 +40,8 @@
           drawHierarchyInKeyWindow: false,
           traits: traits,
           view: viewController.view,
-          viewController: viewController
+          viewController: viewController,
+          delay: delay
         )
       }
     }

Tests/SnapshotTestingTests/DelayTests.swift

@@ -0,0 +1,63 @@
+import XCTest
+@testable import SnapshotTesting
+
+class DelayTests: XCTestCase {
+  func testDelayViewDidLoad() {
+    let  sut = DelayedViewController()
+
+    assertSnapshot(matching: sut, as: .image(on: .iPhone13, delay: 2))
+  }
+  func testViewDidLoad() {
+    let  sut = DelayedViewController()
+
+    assertSnapshot(matching: sut, as: .image(on: .iPhone13))
+  }
+  func testWaitViewDidLoad() {
+      let  sut = DelayedViewController()
+
+    assertSnapshot(matching: sut, as: .wait(for: 2, on: .image(on: .iPhone13)))
+  }
+}
+
+private final class DelayedViewController: UIViewController {
+
+  private lazy var topLabel = UILabel()
+  private lazy var bottomLabel = UILabel()
+
+  override func viewDidLoad() {
+    super.viewDidLoad()
+
+    setupUI()
+
+    DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
+      self.topLabel.text = "Goodbye viewDidLoad"
+    }
+  }
+
+  override func viewDidAppear(_ animated: Bool) {
+    super.viewDidAppear(animated)
+
+    DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
+      self.bottomLabel.text = "Goodbye viewDidAppear"
+    }
+  }
+
+  private func setupUI() {
+    view.backgroundColor = .white
+
+    topLabel.text = "Hello viewDidLoad"
+    bottomLabel.text = "Hello viewDidAppear"
+    topLabel.translatesAutoresizingMaskIntoConstraints = false
+    bottomLabel.translatesAutoresizingMaskIntoConstraints = false
+
+    view.addSubview(topLabel)
+    view.addSubview(bottomLabel)
+
+    NSLayoutConstraint.activate([
+      topLabel.centerXAnchor.constraint(equalTo: view.centerXAnchor),
+      topLabel.centerYAnchor.constraint(equalTo: view.centerYAnchor),
+      bottomLabel.topAnchor.constraint(equalTo: topLabel.bottomAnchor),
+      bottomLabel.centerXAnchor.constraint(equalTo: view.centerXAnchor)
+    ])
+  }
+}