Stub low-RAM model gate in AppState tests

CI free+inactive pages often sit under Medium's 5 GB estimate, so the new pre-load check rejected mock medium loads and broke serialization/restore tests.

Author: jatinkrmalik

Sources/VocaMac/Models/AppState.swift

@@ -324,6 +324,10 @@ final class AppState: ObservableObject {
     /// Set to `true` in tests to avoid side effects.
     let skipSystemIntegration: Bool
 
+    /// Pre-load memory gate. Production defaults to SystemInfo; tests stub this
+    /// so CI free+inactive pages cannot flake medium/large mock loads.
+    var modelFitsInMemory: (ModelSize) -> Bool = { SystemInfo.canFitModelInMemory($0) }
+
     // MARK: - Initialization
 
     init(
@@ -1255,7 +1259,7 @@ final class AppState: ObservableObject {
         // Refuse known-too-large loads before WhisperKit/CoreML can hang the
         // UI spinner under memory pressure (vocamac#250).
         if let targetSize,
-           !SystemInfo.canFitModelInMemory(targetSize) {
+           !modelFitsInMemory(targetSize) {
             let needed = String(format: "%.1f", targetSize.ramRequiredGB)
             let failureMessage =
                 "Not enough free memory to load \(targetSize.displayName) "

Tests/VocaMacTests/AppStateTests.swift

@@ -347,6 +347,43 @@ final class AppStateModelLoadingTests: XCTestCase {
         )
     }
 
+    @MainActor
+    func testLowMemoryGateRefusesMediumBeforeWhisperAndRestoresPrevious() async {
+        UserDefaults.standard.set(ModelSize.small.rawValue, forKey: "vocamac.selectedModelSize")
+
+        let modelManager = MockModelManager()
+        modelManager.downloadedModels = [.small, .medium]
+
+        let whisperService = MockWhisperService()
+        whisperService.loadedModelName = "openai_whisper-small"
+        whisperService.isModelLoaded = true
+        whisperService.loadResponses = [
+            .success("openai_whisper-small"),
+        ]
+
+        let (appState, mocks) = AppState.makeTestState(
+            modelManager: modelManager,
+            whisperService: whisperService
+        )
+        appState.modelFitsInMemory = { $0 != .medium }
+
+        await appState.loadModel(.medium)
+
+        XCTAssertTrue(
+            appState.errorMessage?.contains("Not enough") == true
+                || appState.errorMessage?.localizedCaseInsensitiveContains("free memory") == true
+        )
+        XCTAssertFalse(
+            mocks.whisperService.loadRequests.map { $0.name }.contains("openai_whisper-medium")
+        )
+        XCTAssertEqual(
+            mocks.whisperService.loadRequests.map { $0.name },
+            ["openai_whisper-small"]
+        )
+        XCTAssertEqual(appState.currentModel?.size, .small)
+        XCTAssertEqual(appState.selectedModelSize, ModelSize.small.rawValue)
+    }
+
     @MainActor
     func testDeleteModelRemovesDownloadedModel() async {
         let modelManager = MockModelManager()

Tests/VocaMacTests/Mocks/MockServices.swift

@@ -572,6 +572,8 @@ extension AppState {
             permissionManager: permissionManager,
             skipSystemIntegration: true
         )
+        // Bypass host free-RAM probe so mock loads are not refused on CI.
+        appState.modelFitsInMemory = { _ in true }
         return (appState, mocks)
     }
 }