macos: add test cases for Ghostty.Config properties (#11263)

### AI Disclosure

Test cases is written using the Claude Agent in Xcode

macos/Sources/Ghostty/Ghostty.Config.swift

@@ -53,7 +53,7 @@ extension Ghostty {
         /// - Parameters:
         ///   - path: An optional preferred config file path. Pass `nil` to load the default configuration files.
         ///   - finalize: Whether to finalize the configuration to populate default values.
-        static private func loadConfig(at path: String?, finalize: Bool) -> ghostty_config_t? {
+        static func loadConfig(at path: String?, finalize: Bool) -> ghostty_config_t? {
             // Initialize the global configuration.
             guard let cfg = ghostty_config_new() else {
                 logger.critical("ghostty_config_new failed")

macos/Tests/Ghostty/ConfigTests.swift

@@ -0,0 +1,244 @@
+import Testing
+@testable import Ghostty
+@testable import GhosttyKit
+import SwiftUI
+
+@Suite
+struct ConfigTests {
+    // MARK: - Boolean Properties
+
+    @Test func initialWindowDefaultsToTrue() throws {
+        let config = try TemporaryConfig("")
+        #expect(config.initialWindow == true)
+    }
+
+    @Test func initialWindowSetToFalse() throws {
+        let config = try TemporaryConfig("initial-window = false")
+        #expect(config.initialWindow == false)
+    }
+
+    @Test func quitAfterLastWindowClosedDefaultsToFalse() throws {
+        let config = try TemporaryConfig("")
+        #expect(config.shouldQuitAfterLastWindowClosed == false)
+    }
+
+    @Test func quitAfterLastWindowClosedSetToTrue() throws {
+        let config = try TemporaryConfig("quit-after-last-window-closed = true")
+        #expect(config.shouldQuitAfterLastWindowClosed == true)
+    }
+
+    @Test func windowStepResizeDefaultsToFalse() throws {
+        let config = try TemporaryConfig("")
+        #expect(config.windowStepResize == false)
+    }
+
+    @Test func focusFollowsMouseDefaultsToFalse() throws {
+        let config = try TemporaryConfig("")
+        #expect(config.focusFollowsMouse == false)
+    }
+
+    @Test func focusFollowsMouseSetToTrue() throws {
+        let config = try TemporaryConfig("focus-follows-mouse = true")
+        #expect(config.focusFollowsMouse == true)
+    }
+
+    @Test func windowDecorationsDefaultsToTrue() throws {
+        let config = try TemporaryConfig("")
+        #expect(config.windowDecorations == true)
+    }
+
+    @Test func windowDecorationsNone() throws {
+        let config = try TemporaryConfig("window-decoration = none")
+        #expect(config.windowDecorations == false)
+    }
+
+    @Test func macosWindowShadowDefaultsToTrue() throws {
+        let config = try TemporaryConfig("")
+        #expect(config.macosWindowShadow == true)
+    }
+
+    @Test func maximizeDefaultsToFalse() throws {
+        let config = try TemporaryConfig("")
+        #expect(config.maximize == false)
+    }
+
+    @Test func maximizeSetToTrue() throws {
+        let config = try TemporaryConfig("maximize = true")
+        #expect(config.maximize == true)
+    }
+
+    // MARK: - String / Optional String Properties
+
+    @Test func titleDefaultsToNil() throws {
+        let config = try TemporaryConfig("")
+        #expect(config.title == nil)
+    }
+
+    @Test func titleSetToCustomValue() throws {
+        let config = try TemporaryConfig("title = My Terminal")
+        #expect(config.title == "My Terminal")
+    }
+
+    @Test func windowTitleFontFamilyDefaultsToNil() throws {
+        let config = try TemporaryConfig("")
+        #expect(config.windowTitleFontFamily == nil)
+    }
+
+    @Test func windowTitleFontFamilySetToValue() throws {
+        let config = try TemporaryConfig("window-title-font-family = Menlo")
+        #expect(config.windowTitleFontFamily == "Menlo")
+    }
+
+    // MARK: - Enum Properties
+
+    @Test func macosTitlebarStyleDefaultsToTransparent() throws {
+        let config = try TemporaryConfig("")
+        #expect(config.macosTitlebarStyle == .transparent)
+    }
+
+    @Test(arguments: [
+        ("native", Ghostty.Config.MacOSTitlebarStyle.native),
+        ("transparent", Ghostty.Config.MacOSTitlebarStyle.transparent),
+        ("tabs", Ghostty.Config.MacOSTitlebarStyle.tabs),
+        ("hidden", Ghostty.Config.MacOSTitlebarStyle.hidden),
+    ])
+    func macosTitlebarStyleValues(raw: String, expected: Ghostty.Config.MacOSTitlebarStyle) throws {
+        let config = try TemporaryConfig("macos-titlebar-style = \(raw)")
+        #expect(config.macosTitlebarStyle == expected)
+    }
+
+    @Test func resizeOverlayDefaultsToAfterFirst() throws {
+        let config = try TemporaryConfig("")
+        #expect(config.resizeOverlay == .after_first)
+    }
+
+    @Test(arguments: [
+        ("always", Ghostty.Config.ResizeOverlay.always),
+        ("never", Ghostty.Config.ResizeOverlay.never),
+        ("after-first", Ghostty.Config.ResizeOverlay.after_first),
+    ])
+    func resizeOverlayValues(raw: String, expected: Ghostty.Config.ResizeOverlay) throws {
+        let config = try TemporaryConfig("resize-overlay = \(raw)")
+        #expect(config.resizeOverlay == expected)
+    }
+
+    @Test func resizeOverlayPositionDefaultsToCenter() throws {
+        let config = try TemporaryConfig("")
+        #expect(config.resizeOverlayPosition == .center)
+    }
+
+    @Test func macosIconDefaultsToOfficial() throws {
+        let config = try TemporaryConfig("")
+        #expect(config.macosIcon == .official)
+    }
+
+    @Test func macosIconFrameDefaultsToAluminum() throws {
+        let config = try TemporaryConfig("")
+        #expect(config.macosIconFrame == .aluminum)
+    }
+
+    @Test func macosWindowButtonsDefaultsToVisible() throws {
+        let config = try TemporaryConfig("")
+        #expect(config.macosWindowButtons == .visible)
+    }
+
+    @Test func scrollbarDefaultsToSystem() throws {
+        let config = try TemporaryConfig("")
+        #expect(config.scrollbar == .system)
+    }
+
+    @Test func scrollbarSetToNever() throws {
+        let config = try TemporaryConfig("scrollbar = never")
+        #expect(config.scrollbar == .never)
+    }
+
+    // MARK: - Numeric Properties
+
+    @Test func backgroundOpacityDefaultsToOne() throws {
+        let config = try TemporaryConfig("")
+        #expect(config.backgroundOpacity == 1.0)
+    }
+
+    @Test func backgroundOpacitySetToCustom() throws {
+        let config = try TemporaryConfig("background-opacity = 0.5")
+        #expect(config.backgroundOpacity == 0.5)
+    }
+
+    @Test func windowPositionDefaultsToNil() throws {
+        let config = try TemporaryConfig("")
+        #expect(config.windowPositionX == nil)
+        #expect(config.windowPositionY == nil)
+    }
+
+    // MARK: - Config Loading
+
+    @Test func loadedIsTrueForValidConfig() throws {
+        let config = try TemporaryConfig("")
+        #expect(config.loaded == true)
+    }
+
+    @Test func unfinalizedConfigIsLoaded() throws {
+        let config = try TemporaryConfig("", finalize: false)
+        #expect(config.loaded == true)
+    }
+
+    @Test func defaultConfigIsLoaded() throws {
+        let config = try TemporaryConfig("")
+        #expect(config.optionalAutoUpdateChannel != nil) // release or tip
+        let config1 = try TemporaryConfig("", finalize: false)
+        #expect(config1.optionalAutoUpdateChannel == nil)
+    }
+
+    @Test func errorsEmptyForValidConfig() throws {
+        let config = try TemporaryConfig("")
+        #expect(config.errors.isEmpty)
+    }
+
+    @Test func errorsReportedForInvalidConfig() throws {
+        let config = try TemporaryConfig("not-a-real-key = value")
+        #expect(!config.errors.isEmpty)
+    }
+
+    // MARK: - Multiple Config Lines
+
+    @Test func multipleConfigValues() throws {
+        let config = try TemporaryConfig("""
+        initial-window = false
+        quit-after-last-window-closed = true
+        maximize = true
+        focus-follows-mouse = true
+        """)
+        #expect(config.initialWindow == false)
+        #expect(config.shouldQuitAfterLastWindowClosed == true)
+        #expect(config.maximize == true)
+        #expect(config.focusFollowsMouse == true)
+    }
+}
+
+/// Create a temporary config file and delete it when this is deallocated
+class TemporaryConfig: Ghostty.Config {
+    let temporaryFile: URL
+
+    init(_ configText: String, finalize: Bool = true) throws {
+        let temporaryFile = FileManager.default.temporaryDirectory
+            .appendingPathComponent(UUID().uuidString)
+            .appendingPathExtension("ghostty")
+        try configText.write(to: temporaryFile, atomically: true, encoding: .utf8)
+        self.temporaryFile = temporaryFile
+        super.init(config: Self.loadConfig(at: temporaryFile.path(), finalize: finalize))
+    }
+
+    var optionalAutoUpdateChannel: Ghostty.AutoUpdateChannel? {
+        guard let config = self.config else { return nil }
+        var v: UnsafePointer<Int8>?
+        let key = "auto-update-channel"
+        guard ghostty_config_get(config, &v, key, UInt(key.lengthOfBytes(using: .utf8))) else { return nil }
+        guard let ptr = v else { return nil }
+        let str = String(cString: ptr)
+        return Ghostty.AutoUpdateChannel(rawValue: str)
+    }
+
+    deinit {
+        try? FileManager.default.removeItem(at: temporaryFile)
+    }
+}