从TypeORM迁移至Prisma：单元测试中Prisma函数返回undefined问题

我正从TypeORM迁移到Prisma，单元测试中所有Prisma函数均返回undefined，已采用Prisma官方的依赖注入方案实现。

测试代码 #

const mockCtx2 = createMockContext()
const ctx2 = mockCtx2 as unknown as Context
console.log("createDummyUser")
console.log(ctx2)
console.log(ctx2.prisma)
console.log(ctx2.prisma.users)

控制台输出 #

console.log
  { prisma: { _isMockObject: true } }

    at test/userService.test.ts:889:15

console.log
  { _isMockObject: true }

    at test/userService.test.ts:890:15

console.log
  [Function: mockConstructor] {
    _isMockFunction: true,
    getMockImplementation: [Function (anonymous)],
    mock: [Getter/Setter],
    mockClear: [Function (anonymous)],
    mockReset: [Function (anonymous)],
    mockRestore: [Function (anonymous)],
    mockReturnValueOnce: [Function (anonymous)],
    mockResolvedValueOnce: [Function (anonymous)],
    mockRejectedValueOnce: [Function (anonymous)],
    mockReturnValue: [Function (anonymous)],
    mockResolvedValue: [Function (anonymous)],
    mockRejectedValue: [Function (anonymous)],
    mockImplementationOnce: [Function (anonymous)],
    mockImplementation: [Function (anonymous)],
    mockReturnThis: [Function (anonymous)],
    mockName: [Function (anonymous)],
    getMockName: [Function (anonymous)],
    calledWith: [Function (anonymous)],
    _isMockObject: true
  }

所有Prisma请求均返回undefined，示例：

const allUsers1 = await ctx2.prisma.users.findMany()
console.log(allUsers1) // 输出undefined

更新内容 #

直接使用真实Prisma Client测试可正常返回数据：

import prisma from '../client'

const u = await prisma.users.findMany()
console.log("****")
console.log(u) // 正常输出用户列表

client.ts代码：

import { PrismaClient } from '@prisma/client'

const prisma = new PrismaClient()
export default prisma

问题原因与解决办法 #

问题出在createMockContext生成的是空Mock对象，所有Prisma模型的方法默认未设置返回值，因此调用后返回undefined。真实Client能正常工作说明数据模型和Client配置无问题，仅需完善单元测试的Mock设置。

具体解决步骤 #

1. 为Mock方法指定返回值
   使用mockResolvedValue（异步方法）或mockReturnValue（同步方法）给需要测试的Prisma方法设置模拟数据：

   const mockCtx2 = createMockContext()
   // 为users.findMany设置模拟返回数据
   mockCtx2.prisma.users.findMany.mockResolvedValue([
     { id: 1, username: 'test_user', email: 'test@example.com' }
   ])
   
   const ctx2 = mockCtx2 as unknown as Context
   const allUsers1 = await ctx2.prisma.users.findMany()
   console.log(allUsers1) // 输出模拟的用户数组
   

2. 清理Mock状态避免测试污染
   在每个测试用例执行前清空Mock的调用记录，防止测试间互相干扰：

   beforeEach(() => {
     mockCtx2.prisma.users.findMany.mockClear()
     // 其他需要测试的Prisma方法也需一并清空
   })
   

3. 复杂场景的自定义Mock逻辑
   若需测试条件查询、创建、更新等复杂操作，可使用mockImplementation自定义逻辑：

   mockCtx2.prisma.users.findUnique.mockImplementation(async (args) => {
     // 根据传入的查询参数返回对应模拟数据
     if (args.where.id === 1) {
       return { id: 1, username: 'test_user' }
     }
     return null
   })
   

内容的提问来源于stack exchange，提问作者Marcus