Quit after closing the last app window

src/AppDelegate.swift

@@ -0,0 +1,8 @@
+import AppKit
+
+@MainActor
+final class AppDelegate: NSObject, NSApplicationDelegate {
+    func applicationShouldTerminateAfterLastWindowClosed(_ sender: NSApplication) -> Bool {
+        true
+    }
+}

src/CMakeLists.txt

@@ -1,4 +1,5 @@
 add_executable(SimStore MACOSX_BUNDLE
+    AppDelegate.swift
     SimStoreApp.swift
     ContentView.swift
 )

src/SimStoreApp.swift

@@ -2,6 +2,8 @@ import SwiftUI
 
 @main
 struct SimStoreApp: App {
+    @NSApplicationDelegateAdaptor(AppDelegate.self) private var appDelegate
+
     var body: some Scene {
         WindowGroup("SimStore") {
             ContentView()

tests/AppLifecycleTest.swift

@@ -0,0 +1,32 @@
+import AppKit
+
+@main
+struct AppLifecycleTest {
+    @MainActor
+    static func main() {
+        let application = NSApplication.shared
+        let delegate = AppDelegate()
+        application.delegate = delegate
+        application.setActivationPolicy(.regular)
+
+        let window = NSWindow(
+            contentRect: NSRect(x: 200, y: 200, width: 640, height: 420),
+            styleMask: [.titled, .closable],
+            backing: .buffered,
+            defer: false
+        )
+        window.isReleasedWhenClosed = false
+        window.makeKeyAndOrderFront(nil)
+        DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
+            guard window.isVisible else {
+                fatalError("The test window did not appear.")
+            }
+            print("Closing the last window; the process must exit normally.")
+            window.performClose(nil)
+        }
+        withExtendedLifetime(delegate) {
+            application.run()
+        }
+        fatalError("The application event loop returned without terminating the process.")
+    }
+}

tests/CMakeLists.txt

@@ -5,6 +5,10 @@ target_compile_options(SimStoreSmokeTest PRIVATE -parse-as-library)
 add_test(NAME app-window COMMAND SimStoreSmokeTest "$<TARGET_BUNDLE_DIR:SimStore>")
 set_tests_properties(app-window PROPERTIES TIMEOUT 20 RUN_SERIAL TRUE)
 
+add_executable(SimStoreLifecycleTest AppLifecycleTest.swift "${PROJECT_SOURCE_DIR}/src/AppDelegate.swift")
+add_test(NAME app-window-close COMMAND SimStoreLifecycleTest)
+set_tests_properties(app-window-close PROPERTIES TIMEOUT 10 RUN_SERIAL TRUE)
+
 execute_process(COMMAND xcrun --sdk "${CMAKE_OSX_SYSROOT}" --show-sdk-version
     OUTPUT_VARIABLE SDK_VERSION
     OUTPUT_STRIP_TRAILING_WHITESPACE