Fix so that tests can be run in parallell with Testing (#12)

* Fix so that tests can be run in parallell with Testing

* Fix

* Fix

* Fix

* Rename window

* Fix

* Add log

* Fix

* Clean

Sources/SnapshotTestCase/Snapshot.swift

@@ -166,6 +166,48 @@ private extension Snapshot {
     }
 }
 
+private class SnapshotWindow {
+    static var shared = SnapshotWindow()
+
+    @Published var window: UIWindow?
+
+    @MainActor
+    func new() async throws -> Self {
+        if window == nil {
+            window = UIWindow()
+            return self
+        }
+        for await window in $window.values {
+            if window == nil {
+                break
+            } else {
+                try await Task.sleep(for: .milliseconds(10))
+            }
+        }
+        return try await new()
+    }
+
+    func frame(_ frame: CGRect) -> Self {
+        window?.frame = frame
+        return self
+    }
+
+    func rootViewController(_ viewController: UIViewController) -> Self {
+        window?.rootViewController = viewController
+        return self
+    }
+
+    @MainActor
+    func render(_ render: () async throws -> UIImage) async throws -> UIImage {
+        window?.isHidden = false
+        let snapshot = try await render()
+        window?.isHidden = true
+        window?.removeFromSuperview()
+        window = nil
+        return snapshot
+    }
+}
+
 private extension Snapshot.TestCase {
     private func frame(size: CGSize) -> CGRect {
         CGRect(
@@ -190,11 +232,10 @@ private extension Snapshot.TestCase {
     private func takeSnapshot(with config: SnapshotConfig.Config) async throws -> UIImage {
         let size = config.size + CGSize(width: 0, height: Snapshot.renderOffsetY)
         let (viewController, view) = try create(with: config, in: size)
-        let window = UIWindow(frame: CGRect(origin: .zero, size: size))
-        window.rootViewController = viewController
-        window.makeKeyAndVisible()
-        defer { window.removeFromSuperview() }
-        var snapshot = try await renderSnapshot(view: view, in: size)
+        var snapshot = try await SnapshotWindow.shared.new()
+            .frame(CGRect(origin: .zero, size: size))
+            .rootViewController(viewController)
+            .render { try await renderSnapshot(view: view, in: size) }
         snapshot = try await crop(snapshot, to: size)
         snapshot = try await resize(snapshot, to: Snapshot.renderScale)
         return snapshot
@@ -208,9 +249,7 @@ private extension Snapshot.TestCase {
         }
 
         try await Task.sleep(for: .seconds(renderDelay))
-        await MainActor.run {
-            view.layer.render(in: context)
-        }
+        view.layer.render(in: context)
 
         let image = UIGraphicsGetImageFromCurrentImageContext()
         UIGraphicsEndImageContext()

Tests/SnapshotTestCaseTests/TestingSnapshotTestCaseTests.swift

@@ -0,0 +1,55 @@
+import SnapshotTestCase
+import SwiftUI
+import Testing
+
+@Suite
+class TestingSnapshotTestCaseTests: SnapshotTestCase {
+    @Test
+    func test() async throws {
+        try await verifySnapshot {
+            TestView()
+        }
+    }
+
+    @Test
+    func test2() async throws {
+        try await verifySnapshot(
+            config: SnapshotConfig().add(device: .d6dot1, interfaceStyle: .dark)
+        ) {
+            let viewController = UIHostingController(rootView: TestView())
+            DispatchQueue.main.asyncAfter(deadline: .now() + 0.1) {
+                let subRootView = Rectangle()
+                    .foregroundColor(.green)
+                    .clipShape(RoundedRectangle(cornerSize: .init(width: 32, height: 32)))
+                    .edgesIgnoringSafeArea(.all)
+                guard let subview = UIHostingController(rootView: subRootView).view else {
+                    return
+                }
+                viewController.view.addSubview(subview)
+                subview.frame = viewController.view.bounds
+            }
+            return viewController
+        }
+    }
+}
+
+private struct TestView: View {
+    @Environment(\.colorScheme) var colorScheme
+
+    var body: some View {
+        VStack {
+            switch colorScheme {
+            case .light: Text("Light")
+            case .dark: Text("Dark")
+            @unknown default: Text("Unknown")
+            }
+
+            Rectangle()
+                .foregroundColor(.blue)
+                .clipShape(RoundedRectangle(cornerSize: .init(width: 32, height: 32)))
+
+            Circle().foregroundColor(.yellow)
+        }
+        .edgesIgnoringSafeArea(.all)
+    }
+}

Tests/SnapshotTestCaseTests/SnapshotTestCaseTests.swift → Tests/SnapshotTestCaseTests/XCTestSnapshotTestCaseTests.swift

@@ -30,7 +30,7 @@ class SnapshotTestCaseTests: XCTestCase, SnapshotTestCase {
     }
 }
 
-struct TestView: View {
+private struct TestView: View {
     @Environment(\.colorScheme) var colorScheme
 
     var body: some View {