Nestjs testing module not found

Question

I created a simple REST API using Mongdoose with Nestjs. I have in total 2 tests and they are failing. The test output:

FAIL src/app/auth/auth.service.spec.ts ● Test suite failed to run

Cannot find module '@shared/errors' from 'auth.service.ts'

   5 | 
   6 | import { AppLogger } from '../logger/logger';
>  7 | import { Errors } from '@shared/errors';
     | ^
   8 | import { ILoginDto } from './dto/login.dto';
   9 | import { ITokenDto } from './dto/auth.dto';
  10 | import { IUser } from '@user/document/user.doc';

  at Resolver.resolveModule (../../node_modules/jest-resolve/build/index.js:259:17)
  at Object.<anonymous> (auth/auth.service.ts:7:1)

FAIL src/app/user/user.service.spec.ts ● Test suite failed to run

Cannot find module '@shared/errors' from 'user.service.ts'

  1 | import { BadRequestException, Injectable } from '@nestjs/common';
  2 | import { InjectModel } from '@nestjs/mongoose';
> 3 | import { Errors } from '@shared/errors';
    | ^
  4 | import { createMultipleRandom } from '@shared/utils';
  5 | import { Model } from 'mongoose';
  6 | import { AppLogger } from '../logger/logger';

  at Resolver.resolveModule (../../node_modules/jest-resolve/build/index.js:259:17)
  at Object.<anonymous> (user/user.service.ts:3:1)

Test Suites: 2 failed, 2 total Tests: 0 total Snapshots: 0 total Time: 2.751s Ran all test suites.

tsconfig.json:

{
  "compilerOptions": {
    "module": "commonjs",
    "declaration": true,
    "removeComments": true,
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "target": "es2017",
    "sourceMap": true,
    "outDir": "./dist",
    "baseUrl": "./",
    "incremental": true,
    "paths": {
      "@app/*": ["src/app/*"],
      "@auth/*": ["src/app/auth/*"],
      "@config/*": ["config/*"],
      "@logger/*": ["src/app/logger/*"],
      "@shared/*": ["src/app/shared/*"],
      "@user/*": ["src/app/user/*"],
    }
  },
  "include": [
    "src/**/*"
  ],

  "exclude": ["node_modules", "dist"]
}

auth.service.spec.ts:

import { Test, TestingModule } from '@nestjs/testing';
import { AuthService } from './auth.service';
describe('AuthService', () => {
  let service: AuthService;

  beforeEach(async () => {
    const module: TestingModule = await Test.createTestingModule({
      providers: [AuthService],
    }).compile();

    service = module.get<AuthService>(AuthService);
  });

  it('should be defined', () => {
    expect(service).toBeDefined();
  });
});

In @shared/errors.ts I just export a constant variable. Since it is not a module, how should I import this in a test ? How can I solve this problem ?

Answer 1

As you are using typescript's path mapping, you need to also update your jest config with the mapped paths as well. Your jest config needs to have the following added:

{
  ...
  "moduleNameMapper": {
    "^@Shared/(.)*$": "<rootDir>/src/app/shared/$1"
  }
}

Assuming that your <rootDir> is set to be . and not ./src. You can find more info on it here.

Answer 2

Here is a detailed configurations for jest-path-resolving problem.

The defined keys inside the moduleNameMapper will be replaced with their values.

For example, when jest sees '@resources', it will replace it with 'src/resources'

(Using index file helps a lot)

Jest configuration in the package.json

 "jest": {
    "moduleFileExtensions": [
      "js",
      "json",
      "ts"
    ],
    "rootDir": "src",
    "moduleNameMapper": {
      "@resources": "<rootDir>/resources",
      "@shared": "<rootDir>/shared",
      "@email": "<rootDir>/email",
      "@auth": "<rootDir>/auth",
      "@config": "<rootDir>/config",
      "@database": "<rootDir>/database"
    },
    "testRegex": ".*\\.spec\\.ts$",
    "transform": {
      "^.+\\.(t|j)s$": "ts-jest"
    },
    "collectCoverageFrom": [
      "**/*.(t|j)s"
    ],
    "coverageDirectory": "../coverage",
    "testEnvironment": "node"
  }

Typescript configuration

 "paths": {
      "@resources/*": ["src/resources/*"],
      "@resources": ["src/resources"],
      "@shared/*": ["src/shared/*"],
      "@shared": ["src/shared"],
      "@email/*": ["src/email/*"],
      "@email": ["src/email"]
    }