如何对 Core Data 迁移进行单元测试？

Question

我正在使用自定义实体迁移策略为我的迁移构建一个映射模型，我真的很想为此迁移构建一些单元测试。当我运行应用程序时，迁移似乎正常工作，但是当我通过单元测试运行迁移时，我的 NSEntityMigrationPolicy 子类方法根本没有被调用。

我正在使用 Xcode 的内置 OCUnit 框架。

我的测试代码：

- (void)test1to2Migration_appIdentifierMoved {
  [self createVersion1Store];

  // TODO Perform migration
  NSManagedObjectModel *version1Model = [self version1Model];
  NSManagedObjectModel *version2Model = [self version2Model];

  NSError *error = nil;
  NSMappingModel *mappingModel = [NSMappingModel
      inferredMappingModelForSourceModel:version1Model
      destinationModel:version2Model error:&error];
  STAssertNotNil(mappingModel, @"Error finding mapping model: %@", error);

  NSMigrationManager *migrationManager =
      [[[NSMigrationManager alloc]
        initWithSourceModel:version1Model
        destinationModel:version2Model]
       autorelease];

  BOOL migrationSucceeded =
      [migrationManager migrateStoreFromURL:self.version1StoreURL
           type:NSSQLiteStoreType
           options:nil
           withMappingModel:mappingModel
           toDestinationURL:self.version2StoreURL
           destinationType:NSSQLiteStoreType
           destinationOptions:nil
           error:&error];
  STAssertTrue(migrationSucceeded, @"Error migrating store: %@", error);

  // TODO Verify appIdentifier is moved from Project to its Tests

  [self deleteTempStores];
}

我的映射模型指定了一个自定义的 NSEntityMigrationPolicy，它定义了 -createRelationshipsForDestinationInstance:entityMapping:manager:error: 方法，但我的策略从未从单元测试中调用。当我运行迁移时，模型被修改为新版本——预期的属性显示在正确的位置。

有什么想法可以让我的迁移策略在单元测试中发挥作用吗？

Answer 1

斯威夫特 3

为您的模型文件名替换变量 modelName 和 modelNameVersionFormatString

import XCTest
import CoreData

class RCCoreDataMigrationTests: XCTestCase {

    private let storeType = NSSQLiteStoreType
    private let modelName = "Model"
    private let modelNameVersionFormatString = "Model-%@"

    private func storeURL(_ version: String) -> URL? {
        let storeURL = URL(fileURLWithPath: "\(NSTemporaryDirectory())\(version).sqlite" )
        return storeURL
    }

    private func createObjectModel(_ version: String) -> NSManagedObjectModel? {
        let bundle = Bundle.main
        let managedObjectModelURL = bundle.url(forResource: modelName, withExtension: "momd")
        let managedObjectModelURLBundle = Bundle(url: managedObjectModelURL!)
        let modelVersionName = String(format: modelNameVersionFormatString, version)
        let managedObjectModelVersionURL = managedObjectModelURLBundle!.url(forResource: modelVersionName, withExtension: "mom")
        return NSManagedObjectModel(contentsOf: managedObjectModelVersionURL!)
    }

    private func createStore(_ version: String) -> NSPersistentStoreCoordinator {
        let model = createObjectModel(version)
        let storeCoordinator = NSPersistentStoreCoordinator(managedObjectModel: model!)
        try! storeCoordinator.addPersistentStore(ofType: storeType,
                                                 configurationName: nil,
                                                 at: storeURL(version),
                                                 options: nil)
        return storeCoordinator
    }

    private func migrateStore(fromVersionMOM: String, toVersionMOM: String) {
        let store = createStore(fromVersionMOM)
        let nextVersionObjectModel = createObjectModel(toVersionMOM)!
        let mappingModel = NSMappingModel(from: [Bundle.main], forSourceModel: store.managedObjectModel, destinationModel: nextVersionObjectModel)!
        let migrationManager = NSMigrationManager(sourceModel: store.managedObjectModel, destinationModel: nextVersionObjectModel)
        do {
            try migrationManager.migrateStore(from: store.persistentStores.first!.url!,
                                              sourceType: storeType,
                                              options: nil,
                                              with: mappingModel,
                                              toDestinationURL: storeURL(toVersionMOM)!,
                                              destinationType: NSSQLiteStoreType,
                                              destinationOptions: nil)
        } catch {
            print("Error: \(error)")
            XCTAssertNil(error)
        }
        try! FileManager.default.removeItem(at: storeURL(toVersionMOM)!)
        try! FileManager.default.removeItem(at: storeURL(fromVersionMOM)!)
    }

    func testMigratingStores() {
        migrateStore(fromVersionMOM: "1486", toVersionMOM: "1487")
    }
}

Answer 2

原来问题出在一行

NSMappingModel *mappingModel = [NSMappingModel
  inferredMappingModelForSourceModel:version1Model
  destinationModel:version2Model error:&error];

如果我把它改成

NSMappingModel *mappingModel = [NSMappingModel
  mappingModelFromBundles:@[[NSBundle bundleForClass:[MyTestClass class]]]
  forSourceModel:version1Model destinationModel:version2Model];

然后测试正常运行。