add theme tests

macos/GhosttyUITests/AppKitExtensions.swift

@@ -0,0 +1,34 @@
+//
+//  AppKitExtensions.swift
+//  Ghostty
+//
+//  Created by luca on 27.10.2025.
+//
+
+import AppKit
+
+extension NSColor {
+    var isLightColor: Bool {
+        return self.luminance > 0.5
+    }
+
+    var luminance: Double {
+        var r: CGFloat = 0
+        var g: CGFloat = 0
+        var b: CGFloat = 0
+        var a: CGFloat = 0
+
+        guard let rgb = self.usingColorSpace(.sRGB) else { return 0 }
+        rgb.getRed(&r, green: &g, blue: &b, alpha: &a)
+        return (0.299 * r) + (0.587 * g) + (0.114 * b)
+    }
+}
+
+extension NSImage {
+    func colorAt(x: Int, y: Int) -> NSColor? {
+        guard let cgImage = self.cgImage(forProposedRect: nil, context: nil, hints: nil) else {
+            return nil
+        }
+        return NSBitmapImageRep(cgImage: cgImage).colorAt(x: x, y: y)
+    }
+}

macos/GhosttyUITests/GhosttyThemeTests.swift

@@ -0,0 +1,46 @@
+//
+//  GhosttyThemeTests.swift
+//  Ghostty
+//
+//  Created by luca on 27.10.2025.
+//
+
+import XCTest
+import AppKit
+
+final class GhosttyThemeTests: GhosttyCustomConfigCase {
+
+    /// https://github.com/ghostty-org/ghostty/issues/8282
+    func testIssue8282() throws {
+        try updateConfig("theme=light:3024 Day,dark:3024 Night\ntitle=GhosttyThemeTests")
+        XCUIDevice.shared.appearance = .dark
+
+        let app = try ghosttyApplication()
+        app.launch()
+        let windowTitle = app.windows.firstMatch.title
+        let titleView = app.windows.firstMatch.staticTexts.element(matching: NSPredicate(format: "value == '\(windowTitle)'"))
+
+        let image = titleView.screenshot().image
+        guard let imageColor = image.colorAt(x: 0, y: 0) else {
+            return
+        }
+        XCTAssertLessThanOrEqual(imageColor.luminance, 0.5, "Expected dark appearance for this test")
+        // create a split
+        app.groups["Terminal pane"].typeKey("d", modifierFlags: .command)
+        // reload config
+        app.typeKey(",", modifierFlags: [.command, .shift])
+        // create a new window
+        app.typeKey("n", modifierFlags: [.command])
+
+        for i in 0..<app.windows.count {
+            let titleViewI = app.windows.element(boundBy: i).staticTexts.element(matching: NSPredicate(format: "value == '\(windowTitle)'"))
+
+            let imageI = titleViewI.screenshot().image
+            guard let imageColorI = imageI.colorAt(x: 0, y: 0) else {
+                return
+            }
+
+            XCTAssertLessThanOrEqual(imageColorI.luminance, 0.5, "Expected dark appearance for this test")
+        }
+    }
+}