我正在设置 Jest 来测试 typescript 应用程序。
如何清除模拟函数并恢复其他测试的原始实现?
模拟我使用过的函数:jest.fn().mockImplementationOnce()
到目前为止,我已经在 beforeEach 和 afterEach 中尝试了 jest.clearAll()/resetModules()/resetAllMocks(),但没有成功。
app.test.ts
import App from './app';
import { DbService } from './lib/dbService';
describe('App', () => {
let dbService: DbService;
let app: App;
beforeEach(() => {
jest.clearAllMocks();
dbService = new DbService();
app = new App();
});
describe('getUsers', () => {
it('Should get an array users #1', () => {
expect(app).toBeInstanceOf(App);
const allUsers = app.getAllUsers();
expect(allUsers[0].id).toBeDefined();
});
it('should return an error #2', () => {
DbService.prototype.getAllUsers =
jest.fn().mockImplementationOnce(() => {
return new Error('No connection to DB');
});
expect(app.getAllUsers()).toEqual(new Error('No connection to DB'));
});
it('Should get an array users #3', () => {
expect(app).toBeInstanceOf(App);
const allUsers = app.getAllUsers();
expect(allUsers[0].id).toBeDefined();
});
});
});
app.ts
import { DbService } from './lib/dbService';
export default class App {
private dbService: DbService;
constructor() {
this.dbService = new DbService();
}
getAllUsers() {
return this.dbService.getAllUsers();
}
}
lib/dbService.ts
let instance: DbService;
export class DbService {
constructor() {
if (!instance) {
instance = this;
}
return instance;
}
getAllUsers() {
return [
{id: 1, username: 'john'},
{id: 2, username: 'bill'}
]
}
}
我希望测试 #3 能够像测试 #1 一样通过,但实际上失败并出现以下错误:
FAIL src/app.test.ts
App
getUsers
√ Should get an array users #1 (3ms)
√ should return an error #2 (1ms)
× Should get an array users #3 (1ms)
● App › getUsers › Should get an array users #3
TypeError: Cannot read property '0' of undefined
31 | expect(app).toBeInstanceOf(App);
32 | const allUsers = app.getAllUsers();
> 33 | expect(allUsers[0].id).toBeDefined();
| ^
34 | });
35 | });
36 | });
最佳答案
我不确定这是否是实现此目的的jest
方法,但我认为您可以将原始方法实现保存在变量中,并在每次测试后重新设置该方法,以防万一在测试中被 mock 。
例如
describe('App', () => {
let dbService: DbService;
let app: App;
let originalGetAllUsersFn = DbService.prototype.getAllUsers;
//...
afterEach(() => {
// restore mocked method
DbService.prototype.getAllUsers = originalGetAllUsersFn;
});
});
关于javascript - 如何清除 Jest 模拟实现以进行下一步测试?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/57490718/