Add proper migration tests

Package.swift

@@ -82,6 +82,13 @@ let package = Package(
                 .process("BookmarksModel.xcdatamodeld")
             ]
         ),
+        .executableTarget(name: "BookmarksTestDBBuilder",
+                          dependencies: [
+                            "Bookmarks",
+                            "Persistence"
+                          ],
+                          path: "Sources/BookmarksTestDBBuilder"
+        ),
         .target(
             name: "BookmarksTestsUtils",
             dependencies: [
@@ -234,6 +241,17 @@ let package = Package(
             dependencies: [
                 "Bookmarks",
                 "BookmarksTestsUtils"
+            ],
+            resources: [
+                .copy("Resources/Bookmarks_V1.sqlite"),
+                .copy("Resources/Bookmarks_V1.sqlite-shm"),
+                .copy("Resources/Bookmarks_V1.sqlite-wal"),
+                .copy("Resources/Bookmarks_V2.sqlite"),
+                .copy("Resources/Bookmarks_V2.sqlite-shm"),
+                .copy("Resources/Bookmarks_V2.sqlite-wal"),
+                .copy("Resources/Bookmarks_V3.sqlite"),
+                .copy("Resources/Bookmarks_V3.sqlite-shm"),
+                .copy("Resources/Bookmarks_V3.sqlite-wal")
             ]),
         .testTarget(
             name: "BrowserServicesKitTests",

Sources/Bookmarks/Migrations/BookmarkFormFactorFavoritesMigration.swift

@@ -28,27 +28,32 @@ public class BookmarkFormFactorFavoritesMigration {
     public static func getFavoritesOrderFromPreV4Model(dbContainerLocation: URL,
                                                        dbFileURL: URL,
                                                        errorEvents: EventMapping<MigrationErrors>? = nil) -> [String]? {
-        var oldFavoritesOrder: [String]?
 
-        let metadata = try? NSPersistentStoreCoordinator.metadataForPersistentStore(ofType: NSSQLiteStoreType,
-                                                                                    at: dbFileURL)
-        if let metadata, let version = metadata["NSStoreModelVersionHashesVersion"] as? Int, version < 4 {
-            // Before migrating to latest scheme version, read order of favorites from DB
+        guard let metadata = try? NSPersistentStoreCoordinator.metadataForPersistentStore(ofType: NSSQLiteStoreType, at: dbFileURL),
+              let latestModel = CoreDataDatabase.loadModel(from: bundle, named: "BookmarksModel"),
+              !latestModel.isConfiguration(withName: nil, compatibleWithStoreMetadata: metadata) 
+        else {
+            return nil
+        }
 
-            let v3BookmarksModel = NSManagedObjectModel.mergedModel(from: [Bookmarks.bundle], forStoreMetadata: metadata)!
+        // Before migrating to latest scheme version, read order of favorites from DB
 
-            let oldDB = CoreDataDatabase(name: "Bookmarks",
-                                         containerLocation: dbContainerLocation,
-                                         model: v3BookmarksModel)
-            oldDB.loadStore { context, error in
-                guard let context = context else {
-                    errorEvents?.fire(.couldNotLoadDatabase, error: error)
-                    return
-                }
+        let oldBookmarksModel = NSManagedObjectModel.mergedModel(from: [Bookmarks.bundle], forStoreMetadata: metadata)!
+        let oldDB = CoreDataDatabase(name: dbFileURL.deletingPathExtension().lastPathComponent,
+                                     containerLocation: dbContainerLocation,
+                                     model: oldBookmarksModel)
 
-                let favs = BookmarkUtils.fetchLegacyFavoritesFolder(context)
-                oldFavoritesOrder = favs?.favoritesArray.compactMap { $0.uuid }
+        var oldFavoritesOrder: [String]?
+
+        oldDB.loadStore { context, error in
+            guard let context = context else {
+                errorEvents?.fire(.couldNotLoadDatabase, error: error)
+                return
             }
+
+            let favs = BookmarkUtils.fetchLegacyFavoritesFolder(context)
+            let orderedFavorites = favs?.favorites?.array as? [BookmarkEntity] ?? []
+            oldFavoritesOrder = orderedFavorites.compactMap { $0.uuid }
         }
         return oldFavoritesOrder
     }