CODEWITHSUNDEEP
typescriptunit-testingjestjsprisma
jmecs
jmecs

Reputation: 197

ReferenceError: Cannot access 'jest_mock_extended_1' before initialization

I have the following code.

singleton.ts

import prisma from "../prismaClient";
import { mockDeep, mockReset } from "jest-mock-extended";
import { PrismaClient } from "@prisma/client";
import { DeepMockProxy } from "jest-mock-extended/lib/cjs/Mock";

jest.mock("../prismaClient", () => ({
  __esModule: true,

  default: mockDeep<PrismaClient>(),
}));

beforeEach(() => {
  mockReset(prismaMock);
});

export const prismaMock = prisma as unknown as DeepMockProxy<PrismaClient>;

prismaClient.ts

import { PrismaClient } from "@prisma/client";

const prisma = new PrismaClient({
  log: [
    {
      emit: "event",
      level: "query",
    },
    {
      emit: "stdout",
      level: "error",
    },
    {
      emit: "stdout",
      level: "info",
    },
    {
      emit: "stdout",
      level: "warn",
    },
  ],
});

export default prisma;

I am following prisma's guide to unit testing here: https://www.prisma.io/docs/guides/testing/unit-testing. I don't know why I keep getting this error:

This the error message ReferenceError: Cannot access 'jest_mock_extended_1' before initialization

       7 |   __esModule: true,
       8 |
    >  9 |   default: mockDeep<PrismaClient>(),
         |            ^
      10 | }));
      11 |
      12 | beforeEach(() => {

      at src/utils/testUtils/singleton.ts:9:12
      at Object.<anonymous> (src/utils/testUtils/singleton.ts:1:1)
      at Object.<anonymous> (src/resolvers/functions/user.test.ts:1:1)

Upvotes: 3

Views: 4314

Answers (3)

Edgar Lepe
Edgar Lepe

Reputation: 66

Your issue is probably related to the difference in module mocking when using ESM. See this section in the Jest docs.

So, you need to import your mocked module after you call jest.mock for it to work correctly:

import { mockDeep, mockReset } from "jest-mock-extended";
import { PrismaClient } from "@prisma/client";
import { DeepMockProxy } from "jest-mock-extended";

jest.mock("../prismaClient", () => ({
  __esModule: true,

  default: mockDeep<PrismaClient>(),
}));

import prisma from "../prismaClient";

beforeEach(() => {
  mockReset(prismaMock);
});

export const prismaMock = prisma as unknown as DeepMockProxy<PrismaClient>;

Upvotes: 0

Trevor Martin
Trevor Martin

Reputation: 21

It seemed weird to import a class that you are mocking just to export it. So i created deepMock of PrismaClient, added it to the jest.mock and exported the deepMock.

import { PrismaClient } from '@prisma/client'
import { mockDeep, mockReset, DeepMockProxy } from 'jest-mock-extended'

const prismaMock = mockDeep<PrismaClient>();

jest.mock("../prismaClient", () => ({
  __esModule: true,
  default: prismaMock
}));

beforeEach(() => {
  mockReset(prismaMock);
});

export { prismaMock }

Upvotes: 2

Allen
Allen

Reputation: 182

The issue is that the import path and the path you are mocking are the same. That is import prisma from "../prismaClient"; gets mocked by

jest.mock("../prismaClient", () => ({
  __esModule: true,

  default: mockDeep<PrismaClient>(),
}));

So this means in the file itself mocking happens which triggers that error. If you want this to work then the path you are mocking and the path you are importing here must be different. Something like the below works

import prisma from "../prismaClient";

jest.mock("../../prismaClient", () => ({
  __esModule: true,

  default: mockDeep<PrismaClient>(),
}));

Upvotes: 0

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