テスト自動化と品質担保の強化

- CalendarServiceに対するユニットテスト（ロード、保存の挙動）を実装
- Makefileにtestターゲットを追加し、コマンドラインからテスト実行を可能化
- Xcodeプロジェクト(yml)にテストターゲット（OreCalendarTests）とtest定義を追加

Tests/CalendarServiceTests.swift

@@ -0,0 +1,50 @@
+import XCTest
+import EventKit
+@testable import OreCalendar
+
+@MainActor
+final class CalendarServiceTests: XCTestCase {
+    var service: CalendarService!
+    let testKey = "selectedCalendars"
+
+    override func setUp() async throws {
+        try await super.setUp()
+        service = CalendarService()
+        UserDefaults.standard.removeObject(forKey: testKey)
+    }
+
+    override func tearDown() async throws {
+        UserDefaults.standard.removeObject(forKey: testKey)
+        service = nil
+        try await super.tearDown()
+    }
+
+    func testLoadDefaultSelectedCalendars_withSavedCalendars() async throws {
+        let savedCalendarIDs = ["calendar1", "calendar2", "calendar3"]
+        UserDefaults.standard.set(savedCalendarIDs, forKey: testKey)
+
+        service.loadDefaultSelectedCalendars()
+
+        XCTAssertEqual(service.selectedCalendars, Set(savedCalendarIDs))
+    }
+
+    func testLoadDefaultSelectedCalendars_withoutSavedCalendars() async throws {
+        UserDefaults.standard.removeObject(forKey: testKey)
+
+        service.loadDefaultSelectedCalendars()
+
+        let expectedCalendarIDs = Set(service.availableCalendars.map { $0.calendarIdentifier })
+        XCTAssertEqual(service.selectedCalendars, expectedCalendarIDs)
+    }
+
+    func testSaveSelectedCalendars() async throws {
+        let testCalendarIDs = ["cal1", "cal2", "cal3"]
+        service.selectedCalendars = Set(testCalendarIDs)
+
+        service.saveSelectedCalendars()
+
+        let savedCalendars = UserDefaults.standard.array(forKey: testKey) as? [String]
+        XCTAssertNotNil(savedCalendars)
+        XCTAssertEqual(Set(savedCalendars!), Set(testCalendarIDs))
+    }
+}