Typescript 将Jasmine SpyObj Mock转换为Jest Mock

我正在尝试将我的angular项目测试从Jasmine迁移到Jest。在尝试使用TS Jest mocked方法模拟Angularfire firestore类时，我似乎无法正确理解这一点

我使用jasmine的createSpyObj方法多次实现了这一点

describe('My Example', () => {
    let firestoreSpy: SpyObj<AngularFirestore>;
    let firestoreCollectionSpy: SpyObj<AngularFirestoreCollection>;

    beforeEach(() => {
        firestoreSpy = jasmine.createSpyObj('firestoreSpy', ['collection']);
        firestoreCollectionSpy= jasmine.createSpyObj('firestoreCollectionSpy', ['snapshotChanges']);
        firestoreSpy.collection.and.returnValue(firestoreCollectionSpy);
    });

    it('My Test', () => {
        // Set the return value of the snapshotChanges method
        collectionSpy.snapshotChanges.and.returnValue(of());
    };
});

我得到了一个集合的未定义值，它实际上是AngularFirestore类的一个方法

TypeError: Cannot read property 'mockImplementation' of undefined

任何能让我走上正轨的见解都将不胜感激

TypeError: Cannot read property 'mockImplementation' of undefined