Add CorePlatformImageTests

Author: Kyle-Ye

Tests/OpenSwiftUI_SPITests/Overlay/CoreGraphics/CorePlatformImageTests.swift

@@ -0,0 +1,41 @@
+//
+//  CorePlatformImageTests.swift
+//  OpenSwiftUI_SPITests
+
+#if canImport(Darwin)
+import CoreGraphics
+import Foundation
+import OpenSwiftUI_SPI
+import OpenSwiftUICore
+import Testing
+
+@MainActor
+struct CorePlatformImageTests {
+    @Test
+    func nilCGImage() {
+        let image: NSObject
+        #if os(iOS)
+        image = UIImage()
+        #elseif os(macOS)
+        image = NSImage(size: CGSize(width: 100, height: 100))
+        #endif
+        let coreImage = CorePlatformImage(system: .appKit, kitImage: image)
+        #expect(coreImage.cgImage == nil)
+        #expect(coreImage.size == .zero)
+    }
+    
+    @Test
+    func nonNilCGImage() {
+        let image: NSObject
+        #if os(iOS)
+        image = UIImage.add
+        #elseif os(macOS)
+        image = NSImage(named: NSImage.addTemplateName)!
+        #endif
+        let coreImage = CorePlatformImage(system: .appKit, kitImage: image)
+        #expect(coreImage.cgImage != nil)
+        #expect(coreImage.size != .zero)
+    }
+}
+
+#endif