如何使用Jest在TypeORM中存根EntityManager和连接 [英] How to stub EntityManager and Connection in TypeORM with Jest

问题描述

我使用TypeORM和用Jest编写的单元测试在TypeScript的NestJS上获得了一个应用程序.我有一个使用这样的事务的函数:

I got an app on NestJS in Typescript using TypeORM and unit-tests written with Jest. I have a function that uses transactions like this:

async createMany(users: User[]) {
  await this.connection.transaction(async manager => {
    await manager.save(users[0]);
    await manager.save(users[1]);
  });
}

这是NestJS文档中的一个示例.我通过this.connection.transaction大致以相同的方式进行操作，但是业务逻辑不同.

That's an example from NestJS docs. I do it roughly in the same way via this.connection.transaction but the business-logic is different.

我想做一个单元测试来测试这个服务功能.因此，我需要以某种方式模拟this.connection及其manager.或至少是经理.我不确定如何使用Jest做到这一点.没有连接我就无法创建经理.我无法在没有管理员返回的情况下创建模拟连接.

The thing is I want to make a unit-test to test this service function. So I need to somehow mock both this.connection and its manager. Or at least the manager. I'm not sure how to do it using Jest. I can't create a manager without a connection. I can't create a mock connection with no manager to return inside it.

在NestJS中，同时使用TypeORM和Jest是标准的.必须有一种方法来编写带有事务的单元测试.但是我不确定该怎么做.

Using both TypeORM and Jest is standard in NestJS. There have to be a way to write unit-tests with transactions. But I am not sure how to do it.

请注意，我询问的是单元测试模拟ORM.不是直接使用测试数据库实例的集成测试.

Note that I am asking about unit-test mocking ORM. Not integration tests that would directly use a testing db instance.

推荐答案

您需要使用模拟的Connection创建一个TestingModule.像这样的东西:

You would need to create a TestingModule with a mocked Connection. Something likes this:

import { Test } from "@nestjs/testing";

describe("UsersService", () => {
    let usersService;
    let connection;
    const mockConnection = () => ({
        transaction: jest.fn()
    });

    beforeEach(async () => {
        const module = await Test.createTestingModule({
            providers: [
                UsersService,
                {
                    provide: Connection,
                    useFactory: mockConnection
                }
            ],
        }).compile();

        usersService = await module.get<UsersService>(UsersService); 
        connection = await modle.get<Connection>(Connection);
    });

    describe("some tests", () => {
        it("should test something", async () => {
            const someMockedUsers = [/* some users */];
            const mockedManager = {
                save: jest.fn()
            }
            connection.transaction.mockImplementation((cb) => {
                cb(mockedManager);
            });

            await userService.createMany(someMockedUsers);

            expect(connection.transaction).toHaveBeenCalled();
            expect(mockedManager.save).toHaveBeenCalledTimes(2);
            // ...

        });
    });


});

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